Systems and methods for storage and supply of f3no-free fno gases and f3no-free fno gas mixtures for semiconductor processes

ABSTRACT

Disclosed are systems and methods for supplying a F3NO-free FNO-containing gas and systems and methods for etching using the F3NO-free FNO-containing gas. The system comprises a NiP coated steel cylinder with a polished inner surface to store the F3NO-free FNO-containing gas, a cylinder valve to release the F3NO-free FNO-containing gas from the cylinder, a manifold assembly, including a pressure regulator and line components to deliver the F3NO-free FNO-containing gas to a target reactor. The pressure regulator de-pressurizes the F3NO-free FNO-containing gas in the manifold assembly thereby dividing the manifold assembly into a first pressure zone upstream of the pressure regulator and a second pressure zone downstream of the pressure regulator. A gaseous composition comprises F3NO-free FNO gas containing less than approximately 1% F3NO impurity by volume and an inert gas being capable of suppressing the concentration of F3NO impurity in the F3NO-free FNO gas.

TECHNICAL FIELD

Disclosed are systems and methods for storing and supplying F₃NO-freegas and F₃NO-free gas mixtures, such as, F₃NO-free FNO, F₃NO-freeFNO/N₂, F₃NO-free FNO/F₂, or F₃NO-free FNO/F₂/N₂, or the like, forsemiconductor processes, and systems and methods for using the F₃NO-freegas and F₃NO-free gas mixtures to etch semiconductor structures.

BACKGROUND

Fluorine-containing compounds have been used to etch semiconductormaterials. Nitrosyl fluoride (FNO) is an example of highly reactivefluorinating etching compounds that may be used as a thermal etchinggas.

Various methods have been disclosed to produce FNO. For example, C.Woolf (“Oxyfluoride of Nitrogen”, Adv. Fluorine Chem. 5 (1965), p1-30)discloses using starting materials nitric oxide (NO) and fluorine (F₂)to produce FNO. Using NO as starting material to produce FNO, a trace ofgas impurities of nitrogen oxygen compounds may exist in NO, such asnitrogen dioxide (NO₂), nitrous oxide (N₂O), etc. The reactions involvedin C. Woolf include:

2NO+F₂→2FNO,

N₂O+2F₂→NF₃+FNO,

NF₃+NO→½N₂F₄+FNO.

C. Woolf also discloses the reaction between nitrosyl compound and metalfluoride, such as NOBF₄+NaF→FNO+NaBF₄, to produce FNO. J. H. Holloway etal. (Advances in inorganic chemistry and radiochemistry Vol. 27,p157-195) disclose using fluorination of NOCl by AgF and fluorination ofNO by XeF₂ or XeF₄ to produce FNO along with the methods shown C. Woolf.U.S. Pat. No. 4,996,035 to Stepaniuk et al. discloses mixing nitridewith hydrogen fluoride at mild condition to produce FNO. U.S. Pat. No.3,043,662 to Lipscomb et al. disclose the use of starting materials CF₄or COF₂ and binary oxides of nitrogen, i.e., N₂O, NO, N₂O₃ and NO₂ attemperature larger than 1000° C. with electric arc that produces NF₃,N₂F₂ and FNO.

FNO or FNO gas mixture has been used as etching gas or cleaning agent.For example, WO 2008/117258 to Sonobe et al. discloses a method for lowtemperature thermal cleaning using FNO produced withF_(2 (excess))+NO→F₂+FNO. U.S. Pat. No. 4,536,252 to McDonald et al.discloses FNO is prepared by laser-induced method used to etchsemiconductor surfaces. US 2014/0248783 to Kameda et al. discloses usinga mixture of F₂ and FNO as cleaning agent to remove a deposit in a CVDreaction chamber after forming a film on a substrate, in which FNO isproduced from the reaction of F₂ and NO. US 2013/0220377 to Sato et al.discloses a method of cleaning a film-forming apparatus using F₂ and NOwith heating. U.S. Pat. No. 6,318,384 to Khan et al. discloses aself-cleaning method of forming deep trenches in silicon substratesincluding etching films on semiconductor substrate and cleaning etchchambers with FC compounds including FNO. US 2003/0143846 to Akira etal. discloses a gas composition for cleaning the interior of filmdeposition chambers contaminated with silicic deposition, whichcomprises F₃NO or combinations of F₃NO with O₂ and/or inert gas(es) orwhich comprises FNO or a combination of FNO with O₂ and/or inertgas(es); and also a similar gas composition for etching films ofsilicon-containing compounds, e.g. films of semiconductive materials.

Among these prior arts, the simplest FNO preparation method is thedirect reaction between F₂ and NO, which is expected to have high FNOyield and low impurity generation. However, using F₂ and NO as startingmaterials, depending on reaction conditions, may also produce F₃NO(nitrosyl trifiuoride or trifluoramine oxide), instead of FNO. Forexample, Maxwell et al. (U.S. Pat. No. 3,341,292) disclose a process formaking F₃NO from the reaction between F₂ and NO, in which the feed ratesof F₂ and NO and the proportions of F₂ and NO are regulated so as tomaintain a spontaneous exothermic reaction of F₂ and NO. Maxwell et al.summarized the overall reactions as 1.5F₂+NO→F₃NO+heat, although themechanics of the reactions effected was not understood.

F₃NO has been produced using various starting materials at variousconditions. Bedsides producing F₃NO from the reaction between F₂ and NOas disclosed by Maxwell et al. (U.S. Pat. No. 3,341,292), other startingmaterials are used to produce F₃NO. For example, Fox et al. (U.S. Pat.No. 3,306,834) disclose mixing FNO with F₂ at ultraviolet lightirradiation in the temperature range of 25-50° C. produces F₃NO, i.e.,

Fox et al. (U.S. Pat. No. 3,392,099) also discloses producing F₃NO withstarting materials NF₃ and O₂ at an electrical discharge in the reactionzone of a reactor. Gross et al. (U.S. Pat. No. 3,554,699) disclose F₃NOis prepared by reaction between NF₃ and oxidized oxygen or N₂O in thepresence of a glow discharge, as follows:

NF₃+O₃→F₃NO+O₂

NF₃+N₂O→F₃NO+N₂.

Yonemura et al. (“Evaluation of FNO and F₃NO as Substitute Gases forSemiconductor CVD Chamber Cleaning”, J. Electrochem. Soc. 2003 150(11):G707-G710) (2003)) disclose F₃NO has higher reactivity against Simaterials than FNO, as shown in FIG. 1 reproduced from Yonemura et al.

In addition, it is known that FNO is corrosive which may corrode etchinggas containers and pipelines, etching chambers, substrates to be etched,etc. and lower the semiconductor device performance.

Thus, there are needs to provide a procedure to produce FNO in situ orin close proximity to where it is used to etch semiconductor surfaceswith controlled amount of F₃NO formation and to provide an effectivematerial compatibility for storage and delivery of FNO as well.

SUMMARY

Disclosed are systems for storage and supply of a F₃NO-freeFNO-containing gas. The disclosed systems include a NiP coated steelcylinder with a polished inner surface, configured and adapted to storethe F₃NO-free FNO-containing gas, a cylinder valve, in fluidcommunication with the cylinder, configured and adapted to release theF₃NO-free FNO-containing gas from the cylinder, and a manifold assembly,comprising a pressure regulator and line components, downstream of thecylinder valve, configured and adapted to deliver the F₃NO-freeFNO-containing gas to a target reactor, wherein the pressure regulatoris configured and adapted to de-pressurize the F₃NO-free FNO-containinggas in the manifold assembly so as to divide the manifold assembly intoa first pressure zone upstream of the pressure regulator and a secondpressure zone downstream of the pressure regulator.

Disclosed are methods for storage and supply of a F₃NO-freeFNO-containing gas. The method comprising the steps of: storing theF₃NO-free FNO-containing gas in a NiP coated steel cylinder with apolished inner surface, releasing the F₃NO-free FNO-containing gas fromthe cylinder to a manifold assembly by activating a cylinder valve influid communication with the cylinder and the manifold assembly,de-pressurizing the F₃NO-free FNO-containing gas by activating apressure regulator in the manifold assembly so as to divide the manifoldassembly into a first pressure zone upstream of the pressure regulatorand a second pressure zone downstream of the pressure regulator, andfeeding the de-pressurized F₃NO-free FNO-containing gas to a targetreactor downstream of the second pressure zone.

Also, disclosed are etching systems. The disclosed systems include areactor, configured and adapted to hold therein a substrate to beetched, a NiP coated steel cylinder, configured and adapted to store apressurized etching gas F₃NO-free FNO, a cylinder valve, in fluidcommunication with the cylinder, configured and adapted to release theetching gas F₃NO-free FNO from the NiP coated steel cylinder, and amanifold assembly, comprising a pressure regulator and line components,downstream of the cylinder valve, configured and adapted to deliver theetching gas F₃NO-free FNO to the reactor, wherein the pressure regulatorin the manifold assembly is configured and adapted to de-pressurize theetching gas F₃NO-free FNO so as to divide the manifold assembly into afirst pressure zone upstream of the pressure regulator and a secondpressure zone downstream of the pressure regulator.

Any of the disclosed systems and methods may include one or more of thefollowing aspects:

-   -   the F₃NO-free FNO gas containing less to no F₃NO impurity;    -   the F₃NO-free FNO gas containing less than approximately 1% F₃NO        by volume;    -   the F₃NO-free FNO gas containing less than 0.1% by volume of        F₃NO;    -   the F₃NO-free FNO gas containing less than 0.01% by volume of        F₃NO;    -   the F₃NO-free referring to a gas having F₃NO impurity less than        1%;    -   the F₃NO-free FNO gas contained in the F₃NO-free FNO        gas-containing gas having less than approximately 1% F₃NO by        volume;    -   a pre-synthesized FNO having a purity of 99% or higher;    -   F₂ and NO being starting materials to produce F₃NO-free FNO gas        in situ with the reaction of 2NO+F₂→2FNO;    -   the starting material NO being pure;    -   the starting material NO being between approximately 99.9% by        volume and approximately 100.0% by volume;    -   the starting material NO being between approximately 99.99% by        volume and approximately 100.00% by volume;    -   the starting material NO being between approximately 99.999% by        volume and approximately 100.000% by volume;    -   the starting material NO gas containing between approximately        0.0% by volume and approximately 0.1% % by volume trace gas        impurities with between approximately 0 ppm by volume to        approximately 600 ppm by volume of N—O containing gases other        than NO gas;    -   the starting material NO gas containing between approximately        0.0% by volume and approximately 0.1% % by volume trace gas        impurities with between approximately 0 ppm by volume to        approximately 600 ppm by volume of NO₂;    -   the starting material NO gas containing between approximately        0.0% by volume and approximately 0.1% % by volume trace gas        impurities with between approximately 0 ppm by volume to        approximately 600 ppm by volume of N₂O,    -   mixing F₂ and NO at a ratio F₂/NO under or less than stoicmetric        condition (F₂/NO≤½);    -   the F₃NO-free FNO gas diluted in an inert gas, such as N₂, Ar,        He, Ne, Kr, Xe, or mixtures thereof, to obtain a concentration        of F₃NO-free FNO gas as needed;    -   the F₃NO-free FNO gas diluted in N₂ to obtain a concentration of        F₃NO-free FNO gas as needed;    -   the concentration of F₃NO-free FNO gas in N₂ ranging from 0.01%        to 80%;    -   the concentration of F₃NO-free FNO gas in N₂ ranging from 0.01%        to 30%;    -   the concentration of F₃NO-free FNO gas in N₂ being 3%;    -   the concentration of F₃NO-free FNO gas in N₂ being 15%;    -   the F₃NO-free FNO gas mixture being a gas mixture of F₃NO-free        FNO/F₂/N₂;    -   the concentration of F₃NO-free FNO gas in F₃NO-free FNO/F₂/N₂        gas mixture ranging from 0.01% to 80%;    -   the concentration of F₃NO-free FNO gas in F₃NO-free FNO/F₂/N₂        gas mixture ranging from 0.01% to 30%;    -   the concentration of F₃NO-free FNO gas in F₃NO-free FNO/F₂/N₂        gas mixture being 3%;    -   the concentration of F₃NO-free FNO gas in F₃NO-free FNO/F₂/N₂        gas mixture being 15%;    -   the concentration of F₂ in F₃NO-free FNO/F₂/N₂ gas mixture        ranging from 0% to 80%;    -   the concentration of F₂ in F₃NO-free FNO/F₂/N₂ gas mixture        ranging from 0% to 20%;    -   the concentration of F₂ in F₃NO-free FNO/F₂/N₂ gas mixture being        0%;    -   the concentration of F₂ in F₃NO-free FNO/F₂/N₂ gas mixture being        10%;    -   the concentration of F₃NO-free FNO gas in the gas mixture of        FNO/F₂/N₂ being 15% and the concentration of F₂ in the gas        mixture of FNO/F₂/N₂ being 10%;    -   producing the gas mixture of FNO/F₂/N₂ with a two-step of F₂        mixing process;    -   the two-step of F₂ mixing process including i) F₂ and NO are        mixed under or less than stoicmetric condition (F₂/NO≤½) to        produce F₃NO-free FNO gas and ii) additional F₂ is added to the        produced F₃NO-free FNO gas;    -   the two-step of F₂ mixing process suppressing the formation of        F₃NO;    -   the F₃NO-free FNO gas and the F₃NO-free FNO gas mixture being        stored in a NiP coated steel cylinder;    -   the NiP coated steel cylinder being a carbon steel cylinder made        of steel;    -   the NiP coated steel cylinder being a carbon steel cylinder made        of an alloy 4130X;    -   the NiP coated steel cylinder being a carbon steel cylinder made        of an alloy 4130X with NiP coated inner surface;    -   the NiP coated inner surface of the NiP coated steel cylinder        being polished;    -   the cylinder valve in fluid communication with the NiP coated        steel cylinder being made of nickel material;    -   the cylinder valve in fluid communication with the NiP coated        steel cylinder being made of nickel alloy;    -   the cylinder valve in fluid communication with the NiP cylinder        being made of nickel alloy having nickel content at least 14% by        weight;    -   the cylinder valve being a Ceodeux D306 Ni body Ni disphragm;    -   the manifold assembly divided into a first pressure zone and a        second pressure zone by the pressure regulator;    -   the pressure in the first pressure zone being larger than the        pressure in the second pressure zone;    -   the pressure in the first pressure zone ranging from 0.8 MPa to        3.5 MPa;    -   the pressure in the first pressure zone being 0.99 MPa;    -   the pressure in the second pressure zone ranging from 0.1 MPa to        0.8 MPa;    -   the pressure in the first pressure zone being 0.5 MPa;    -   the line components in the first pressure zone being composed of        high nickel content materials;    -   the line components in the first pressure zone being composed of        MONEL®;    -   the line components in the first pressure zone being composed of        INCONEL®;    -   the line components in the first pressure zone being composed of        HASTELLOY® C-22® alloy;    -   the high nickel content material containing at least 14% nickel        by weight;    -   the line components in the first pressure zone not being        composed of Fe-containing alloy;    -   the line components in the first pressure zone not being        composed of stainless steel (SS);    -   the line components in the first pressure zone not being        composed of Mn-steel;    -   the line components in the second pressure zone being composed        of low nickel content material that contains less than 14%        nickel by weight;    -   the line components in the second pressure zone being composed        of low nickel content material that contains no nickel;    -   the line components in the second pressure zone being composed        of any metal or mental alloy;    -   the line components in the second pressure zone is made of a        metal or a meal alloy;    -   the line components in the second pressure zone being composed        of stainless steel;    -   the stainless steel being SS316L;    -   the SS316L containing up to 14% nickel;    -   the SS316L being compatible with F₃NO-only;    -   the SS316L being not compatible with F₃NO-free FNO/F₂/N₂;    -   the SS316L being compatible with F₃NO-free FNO/F₂/N₂ in the        second pressure zone after passivation using F₂ or FNO;    -   the SS316L being suitable for making the line components in the        second pressure zone if the etching gas does not contains F₂;    -   the F₃NO-free FNO gas-containing gas being selected from the        group consisting of F₃NO-free FNO gas, a mixture of the        F₃NO-free FNO gas with an inert gas, a mixture of the F₃NO-free        FNO gas with an additional gas and a mixture of the F₃NO-free        FNO gas with the inert gas and the additional gas;    -   the F₃NO-free FNO gas-containing gas being F₃NO-free FNO gas;    -   the F₃NO-free FNO gas-containing gas being a mixture of the        F₃NO-free FNO gas with an inert gas;    -   the F₃NO-free FNO gas-containing gas being a mixture of the        F₃NO-free FNO gas with an additional gas;    -   the F₃NO-free FNO gas-containing gas being a mixture of the        F₃NO-free FNO gas with the inert gas and the additional gas;    -   the F₃NO-free FNO gas mixture being selected from the group        consisting of F₃NO-free FNO gas, a mixture of the F₃NO-free FNO        gas with an inert gas, a mixture of the F₃NO-free FNO gas with        an additional gas and a mixture of the F₃NO-free FNO gas with        the inert gas and the additional gas;    -   the F₃NO-free FNO gas mixture being F₃NO-free FNO gas;    -   the F₃NO-free FNO gas mixture being a mixture of the F₃NO-free        FNO gas with an inert gas;    -   the F₃NO-free FNO gas mixture being a mixture of the F₃NO-free        FNO gas with an additional gas;    -   the F₃NO-free FNO gas mixture being a mixture of the F₃NO-free        FNO gas with the inert gas and the additional gas;    -   the inert gas being N₂, Ar, He, Ne, Kr, Xe, or mixtures thereof;    -   the inert gas being N₂;    -   the additional gas being selected from the group consisting of        F₂, HF, cC₄F₈, C₄F₈, C₄F₆, C₅F₈, CF₄, CH₃F, CF₃H, CH₂F₂, COS,        CS₂, CF₃I, C₂F₃I, C₂F₅I, CFN, SO₂, NO, O₂, CO₂, CO, NO₂, N₂O,        O₃, Cl₂, H₂, HBr, and combination thereof;    -   the additional gas being F₂;    -   oxidizer being added to the F₃NO-free FNO gas or the F₃NO-free        FNO gas-containing gas mixture;    -   the oxidizer being O₂, O₃, CO, CO₂, COS, NO, N₂O, NO₂, SO₂, and        combinations thereof;    -   the oxidizer and the F₃NO-free FNO gas or the F₃NO-free FNO        gas-containing gas mixture being mixed together prior to        introduction into the reaction chamber or the etching chamber;    -   The oxidizer comprising between approximately 0.01% by volume to        approximately 99.99% by volume of the mixture introduced into        the chamber (with 99.99% by volume representing introduction of        almost pure oxidizer for the continuous introduction        alternative);    -   the oxidizer being introduced continuously into the reaction        chamber and the etching gas being introduced into the reaction        chamber in pulses;    -   producing F₃NO-free FNO gas contained in the F₃NO-free FNO        gas-containing gas by mixing NO and F₂ gases at a ratio of F₂        gas to NO gas less than or equal to ½ and a purity of NO gas at        least 99.9% by volume, wherein the produced F₃NO-free FNO gas        contains less than approximately 1% F₃NO;    -   producing a gas mixture of F₃NO-free FNO gas, F₂ and N₂ by a        two-step F₂ mixing procedure comprising the steps of        -   mixing F₂ and NO at a ratio of F₂/NO less than or equal to ½            and a purity of NO at least 99.9% by volume to produce the            F₃NO-free FNO gas;        -   mixing the produced F₃NO-free FNO gas with an additional            amount of F₂ to produce the gas mixture of the F₃NO-free FNO            gas and F₂; and        -   diluting the gas mixture of the F₃NO-free FNO gas and F₂ in            N₂ to form the gas mixture of F₃NO-free FNO gas, F₂ and N₂;    -   passivating the manifold assembly with F₂;    -   passivating the manifold assembly with FNO;    -   passivating the first pressure zone of the manifold assembly        with F₂;    -   passivating the first pressure zone of the manifold assembly        with FNO;    -   passivating the second pressure zone of the manifold assembly        with F₂;    -   passivating the second pressure zone of the manifold assembly        with FNO;    -   a first gas line parallel to the manifold assembly;    -   the first gas line feeding an additional etching gas to the        etching chamber, where in the additional etching gas is selected        from the group consisting of F₂, HF, cC₄F₈, C₄F₈, C₄F₆, C₅F₈,        CF₄, CH₃F, CF₃H, CH₂F₂, COS, CS₂, CF₃I, C₂F₃I, C₂F₅I, CFN, SO₂,        NO, O₂, CO₂, CO, NO₂, N₂O, O₃, Cl₂, H₂, HBr, and combination        thereof;    -   the first gas line feeding an additional etching gas to the NiP        coated steel cylinder, where in the additional etching gas is        selected from the group consisting of F₂, HF, cC₄F₈, C₄F₈, C₄F₆,        C₅F₈, CF₄, CH₃F, CF₃H, CH₂F₂, COS, CS₂, CF₃I, C₂F₃I, C₂F₅I, CFN,        SO₂, NO, O₂, CO₂, CO, NO₂, N₂O, O₃, Cl₂, H₂, HBr, and        combination thereof;    -   the first gas line feeding F₂;    -   the F₃NO-free FNO etching gas and the additional gas (e.g., F₂)        being mixed prior to introduction to the reaction chamber;    -   a second gas line for feeding an inert gas to the first pressure        zone of the manifold assembly, wherein the F₃NO-free FNO gas is        mixed with the inert gas to produce a diluted F₃NO-free FNO gas,        wherein the inert gas is N₂, Ar, He, Ne, Kr, Xe, or mixtures        thereof;    -   a second gas line for feeding N₂ to the first pressure zone of        the manifold assembly;    -   a second gas line for feeding an inert gas to NiP coated steel        cylinder, wherein the F₃NO-free FNO gas is mixed with the inert        gas to produce a diluted F₃NO-free FNO gas, wherein the inert        gas is N₂, Ar, He, Ne, Kr, Xe, or mixtures thereof;    -   a second gas line for feeding N₂ to NiP coated steel cylinder;    -   the F₃NO-free FNO gas in the gas cylinder contains the inert        gas;    -   the F₃NO-free FNO gas in the gas cylinder contains N₂;    -   the etching process being thermal etching process;    -   the etching process being plasma dry etching process;    -   the etching chamber being heated to a temperature;    -   a temperature of the etching chamber ranging from 20° C. to        1000° C.;    -   a temperature of the etching chamber ranging from room        temperature to 1000° C.;    -   a temperature of the etching chamber ranging from 100° C. to        600° C.;    -   a temperature of the etching chamber ranging from 100° C. to        300° C.;    -   a temperature of the etching chamber being 100° C.;    -   a temperature of the etching chamber being 500° C.;    -   a temperature of the etching chamber being 600° C.;    -   a pressure in the first pressure zone ranging from 0.8 MPa to        3.5 MPa;    -   a pressure in the second pressure zone ranging from 0.1 MPa to        0.8 MPa;    -   a pressure in the first pressure zone being 0.99 MPa;    -   a pressure in the second pressure zone being 0.5 MPa;    -   a pressure in the etching chamber ranges from approximately 0.1        mTorr and approximately 1000 Torr;    -   a flow rate of F₃NO-free FNO containing etching gas ranging from        approximately 0.1 sccm to approximately 30 slm;    -   The reaction chamber being a thermal etching chamber;    -   The reaction chamber being a plasma etching chamber;    -   The reaction chamber being a deposition chamber;    -   the substrate in the reactor containing a film to be etched;    -   the substrate in the etching chamber containing a film to be        etched;    -   an inner surface of the reactor containing deposits to be        etched;    -   the inner surface of the reactor containing a film to be etched;    -   an inner surface of the deposition chamber containing a layer of        deposits on the inner surface to be etched or removed;    -   the inner surface of the deposition chamber containing a film on        the inner surface to be etched or removed;    -   an inner surface of the deposition chamber containing a layer of        deposits on the inner surface to be cleaned;    -   the inner surface of the deposition chamber containing a film on        the inner surface to be cleaned;    -   the line components in the first pressure zone including gas        filters, pressure sensors, pressure regulator, gas valves,        pipes, and combinations thereof;    -   the line components in the second pressure zone including gas        filters, pressure sensors, gas valves, mass flow controllers        (MFCs), pipes, and combinations thereof;    -   the high nickel content material being a nickel alloy having at        least 14% nickel by weight;    -   the high nickel content material being pure nickel;    -   the high nickel content material being nickel alloys;    -   the high nickel content material being MONEL®, INCONEL® or        HASTELLOY® C-22® alloy;    -   the low nickel content material being a nickel alloy having less        than 14% nickel by weight; and    -   the low nickel content material being stainless steel;

Also, disclosed is a gaseous composition for semiconductor applications.The gaseous composition comprises F₃NO-free FNO gas containing less thanapproximately 1% F₃NO impurity by volume; and an inert gas being capableof suppressing the concentration of F₃NO impurity in the F₃NO-free FNOgas. The disclosed gas composition include one or more of the followingaspects:

-   -   the F₃NO-free FNO gas containing less than approximately 1% F₃NO        impurity by volume;    -   the inert gas beingN₂, Ar, He, Ne, Kr, Xe, or mixtures thereof;    -   the inert gas being N₂;    -   the inert gas being capable of suppressing the concentration of        F₃NO impurity in the F₃NO-free FNO gas;    -   N₂ being capable of suppressing the concentration of F₃NO        impurity in the F₃NO-free FNO gas;    -   the F₃NO-free FNO gas having a purity of 99% by volume;    -   the F₃NO-free FNO gas having a purity ranging from approximately        99% to approximately 99.999% by volume;    -   the F₃NO-free FNO gas containing less than 1% by volume trace        gas impurities;    -   the trace gas impurities comprising water;    -   the trace gas impurities comprising NO₂;    -   the trace gas impurities comprising N₂O,    -   the trace gas impurities comprising F₃NO;    -   the F₃NO-free FNO gas containing less than 1% by volume of F₃NO;        and    -   the F₃NO-free FNO gas having a water content of less than 20        ppmw.

Notation and Nomenclature

The following detailed description and claims utilize a number ofabbreviations, symbols, and terms, which are generally well known in theart, and include:

As used herein, the indefinite article “a” or “an” means one or more.

As used herein, “about” or “around” or “approximately” in the text or ina claim means±10% of the value stated.

As used herein, “less to no” in the text or a claim means the valuestated having a range from approximately 1% to nil.

As used herein, “room temperature” in the text or in a claim means fromapproximately 20° C. to approximately 25° C.

The term “ambient temperature” refers to an environment temperatureapproximately 20° C. to approximately 25° C.

The term “F₃NO-free” or “F₃NO-less” refers to a gas mixture containsless than 1% F₃NO impurity.

The trademark “HASTELLOY®” refers to a family of nickel-based steelalloys exhibiting high resistance to corrosion. HASTELLOY® is anickel-molybdenum alloy. There are a hundred different Hastelloy® alloysmarked B, C, D, M, NS, W, X . . . 22 letters sometimes numbered by a fewnumbers. There are many different grades of Hastelloy®, many of whichare nickel-chromium-molybdenum alloys. Each of these grades has beenoptimized for a specific purpose, but all of them are highly resistantto corrosion. HASTELLOY® has outstanding resistance to highly oxidizingand reducing agents, making it a great choice for moderate to severecorrosive environments. The most versatile of the HASTELLOY® alloy arethe “C-type” alloys, such as, HASTELLOY® C-22® alloy.

The trademark “HASTELLOY® C-22® alloy” refers to one of the well-knownand well-proven nickel-chromium-molybdenum materials, the chiefattributes of which are resistance to both oxidizing and non-oxidizingchemicals, and protection from pitting, crevice attack, and stresscorrosion cracking. The composition of nickel in HASTELLOY® C-22® alloyis 56% by weight.

The trademark “MONEL®” refers to a group of nickel alloys, primarilycomposed of nickel and copper, with small amounts of iron, manganese,carbon, and silicon. Stronger than pure nickel, MONEL® alloys areresistant to corrosion by many agents, including rapidly flowingseawater. The composition of nickel in MONEL® is 63-65% or even up to67% by weight.

The trademark “INCONEL®” refers to a family of nickel-iron-chromiumsuperalloys. There are also many different grades of INCOLOY® available.INCONEL® alloys are oxidation-corrosion-resistant materials well suitedfor service in extreme environments subjected to pressure and heat.INCONEL® retains strength over a wide temperature range, attractive forhigh temperature applications. INCONEL® is a material that isspecifically optimized for some of the toughest use conditions to befound in manufacturing. INCONEL®s high temperature strength andresistance to seawater, brine, sour gas, and chloride make it ideal foruse in the oil and gas industries. The composition of nickel in INCONEL®is 50-80% nickel by weight.

The term “high nickel content material” refers to nickel alloys thatcontains at least 14% nickel by weight.

The term “low nickel content material” refers to a material containsless than 14% nickel by weight or contains no nickel.

The term “stainless steel 316 (SS316)” or “steel use stainless 316(SUS316)” (SUS, an acronym from Japanese Industrial Standards (JIS))refers to a marine grade stainless steel, called type 316, is resistantto certain types of interactions. There are a variety of different typesof 316 stainless steels, including 316 L, F, N, H, and several others.Each has different Ni content. The “L” designation means SS316L has lesscarbon than SS316. The SS316L contains up to 14% Ni.

The term “Ceodeux D306” refers to a high-pressure cylinder valve, whichis a tied diaphragm seal type and used for ultra high purity gases(e.g., purity 99.999%) with main body material made of Nickel andHASTELLOY®.

The term “alloy 4130X” refers to an alloy in a 41xx steel family of SAEsteel grades, as specified by the Society of Automotive Engineers (SAE).Alloying elements include chromium and molybdenum, and as a result,these materials are often informally referred to as chromyl steel.

The term of “metal” refers to a solid material that is typically hard,shiny, malleable, fusible, and ductile, with good electrical and thermalconductivity. A metal may be a chemical element such as iron, gold,silver, copper, and aluminum, or an alloy such as stainless steel.

The term of “metal alloy” refers to a metal made by a combination ofmetals or of a metal and another element. An alloy may be a solidsolution of metal elements or a mixture of metallic phases.

The term “etching system” refers to a system that removing (i.e.,etching or cleaning) a film happens inside a reaction chamber. Thereaction chamber may be a thermal or a plasma etching chamber or adeposition chamber. The film may be on a substrate with a substrateholder placed inside of the etching chamber, which refers to an etchingprocess. The film may be a layer of deposits on the inner surface of thedeposition chamber that needs to be removed. Removing the layer ofdeposits on the inner surface of the deposition chamber also refers to acleaning process.

The term “NiP coated steel cylinder” refers to a steel cylinder with aninternal surface coating of nickel plating (NiP) in which an internalsurface of the NiP is polished. The steel cylinder may be a carbon steelcylinder made of alloy 4130X.

The term “polish” or “polished” refers to making a surface smooth andglossy by mechanical or electro-mechanical polishing.

The term “substrate” refers to a material or materials on which aprocess is conducted. The substrate may refer to a wafer having amaterial or materials on which a process is conducted. The substratesmay be any suitable wafer used in semiconductor, photovoltaic, flatpanel, or LCD-TFT device manufacturing. The substrate may also have oneor more layers of differing materials already deposited upon it from aprevious manufacturing step. For example, the wafers may include siliconlayers (e.g., crystalline, amorphous, porous, etc.), silicon containinglayers (e.g., SiO₂, SiN, SiON, SiCOH, etc.), metal containing layers(e.g., copper, cobalt, ruthenium, tungsten, platinum, palladium, nickel,ruthenium, gold, etc.) or combinations thereof. Furthermore, thesubstrate may be planar or patterned. The substrate may be an organicpatterned photoresist film. The substrate may include layers of oxideswhich are used as dielectric materials in MEMS, 3D NAND, MIM, DRAM, orFeRam device applications (for example, ZrO₂ based materials, HfO₂ basedmaterials, TiO₂ based materials, rare earth oxide based materials,ternary oxide based materials, etc.) or nitride-based films (forexample, TaN, TiN, NbN) that are used as electrodes. One of ordinaryskill in the art will recognize that the terms “film” or “layer” usedherein refer to a thickness of some material laid on or spread over asurface and that the surface may be a trench or a line. Throughout thespecification and claims; the wafer and any associated layers thereonare referred to as substrates.

The term “wafer” or “patterned wafer” refers to a wafer having a stackof silicon-containing films on a substrate and a patterned hardmasklayer on the stack of silicon-containing films formed for pattern etch.

The term “pattern etch” or “patterned etch” refers to etching anon-planar structure, such as a stack of silicon-containing films belowa patterned hardmask layer.

As used herein, the term “etch” or “etching” refers to an isotropicetching process and/or an anisotropic etching process. The isotropicetch process involves a chemical reaction between the etching compoundand the substrate resulting in part of material on the substrate beingremoved. The etching processes may be multiple processes and the etchingprocesses may involve in a surface reaction to modify the surface in thefirst step and in the second step a removal of the modified surfacelayer. This type of etching process includes chemical dry etching, vaporphase chemical etching, thermal dry etching, or the like. The isotropicetch process produces a lateral or horizontal etch profile in asubstrate. The isotropic etch process produces recesses or horizontalrecesses on a sidewall of a pre-formed aperture in a substrate. Theanisotropic etch process involves a plasma etching process (i.e., a dryetch process) in which ion bombardment accelerates the chemical reactionin the vertical direction so that vertical sidewalls are formed alongthe edges of the masked features at right angles to the substrate (Manosand Flamm, Thermal etching an Introduction, Academic Press, Inc. 1989pp. 12-13). The plasma etching process produces a vertical etch profilein a substrate. The plasma etching process produces vertical apertures,trenches, channel holes, gate trenches, staircase contacts, capacitorholes, contact holes, etc., in the substrate.

The term “selectivity” means the ratio of the etch rate of one materialto the etch rate of another material. The term “selective etch” or“selectively etch” means to etch one material more than anothermaterial, or in other words to have a greater or less than 1:1 etchselectivity between two materials.

Note that herein, the terms “film” and “layer” may be usedinterchangeably. It is understood that a film may correspond to, orrelated to a layer, and that the layer may refer to the film.Furthermore, one of ordinary skill in the art will recognize that theterms “film” or “layer” used herein refer to a thickness of somematerial laid on or spread over a surface and that the surface may rangefrom as large as the entire wafer to as small as a trench or a line.

Note that herein, the terms “etching compound” and “etching gas” may beused interchangeably when the etching compound is in a gaseous state atroom temperature and ambient pressure. It is understood that an etchingcompound may correspond to, or related to an etching gas, and that theetching gas may refer to the etching compound.

As used herein, the abbreviation “NAND” refers to a “Negated AND” or“Not AND” gate; the abbreviation “2D” refers to 2 dimensional gatestructures on a planar substrate; the abbreviation “3D” refers to 3dimensional or vertical gate structures, wherein the gate structures arestacked in the vertical direction.

The standard abbreviations of the elements from the periodic table ofelements are used herein. It should be understood that elements might bereferred to by these abbreviation (e.g., Si refers to silicon, N refersto nitrogen, O refers to oxygen, C refers to carbon, H refers tohydrogen, F refers to fluorine, etc.).

The unique CAS registry numbers (i.e., “CAS”) assigned by the ChemicalAbstract Service are provided to identify the specific moleculesdisclosed.

Please note that the silicon-containing films, such as SiN and SiO, arelisted throughout the specification and claims without reference totheir proper stoichiometry. The silicon-containing films may includepure silicon (Si) layers, such as crystalline Si, poly-silicon (p-Si orpolycrystalline Si), or amorphous silicon; silicon nitride (Si_(k)N_(l))layers; or silicon oxide (Si_(n)O_(m)) layers; or mixtures thereof,wherein k, l, m, and n, inclusively range from 0.1 to 6. Preferably,silicon nitride is Si_(k)N_(l), where k and l each range from 0.5 to1.5. More preferably silicon nitride is Si₃N₄. Herein, SiN in thefollowing description may be used to represent Si_(k)N_(l) containinglayers. Preferably silicon oxide is Si_(n)O_(m), where n ranges from 0.5to 1.5 and m ranges from 1.5 to 3.5. More preferably, silicon oxide isSiO₂. Herein, SiO in the following description may be used to representSi_(n)O_(m) containing layers. The silicon-containing film could also bea silicon oxide based dielectric material such as organic based orsilicon oxide based low-k dielectric materials such as the Black DiamondII or III material by Applied Materials, Inc. with a formula of SiOCH.Silicon-containing film may also include Si_(a)O_(b)N_(c) where a, b, crange from 0.1 to 6. The silicon-containing films may also includedopants, such as B, C, P, As and/or Ge.

Ranges may be expressed herein as from about one particular value,and/or to about another particular value. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value and/or to the other particular value, along withall combinations within said range.

Reference herein to “one embodiment” or “an embodiment” means that aparticular feature, structure, or characteristic described in connectionwith the embodiment may be included in at least one embodiment of theinvention. The appearances of the phrase “in one embodiment” in variousplaces in the specification are not necessarily all referring to thesame embodiment, nor are separate or alternative embodiments necessarilymutually exclusive of other embodiments. The same applies to the term“implementation.”

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the presentinvention, reference should be made to the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich like elements are given the same or analogous reference numbersand wherein:

FIG. 1, reproduced from Yonemura et al., represents the etch rates as afunction of gas concentration for FNO/Ar, F₃NO/Ar, NF₃/Ar and C₂F₆/O₂,

FIG. 2 is a diagram of an exemplary packaging of F₃NO-free FNO gasand/or F₃NO-free FNO gas mixture from a cylinder to a semiconductorapplication chamber;

FIG. 3(a) is an order of mixing F₂, NO and N₂ to produce FNO in N₂;

FIG. 3(b) is another order of mixing F₂, NO and N₂ to produce FNO in N₂;

FIG. 3(c) is another order of mixing F₂, NO and N₂ to produce FNO in N₂;

FIG. 3(d) is another order of mixing F₂, NO and N₂ to produce FNO in N₂;

FIG. 4 is a comparison of FT-IR spectra of F₃NO impurity in 30% FNO inN₂ produced from on-site synthesis under stoichiometric condition versus30% FNO in N₂ produced from on-site synthesis under F₂-rich condition;

FIG. 5(a) is an order of mixing F₂, NO and N₂ to produce a gas mixtureof F₃NO-free FNO/F₂/N₂;

FIG. 5(b) is another order of mixing F₂, NO and N₂ to produce F₃NO-freeFNO/F₂/N₂ gas mixture;

FIG. 5(c) is another order of mixing F₂, NO and N₂ to produce a gasmixture of F₃NO-free FNO/F₂/N₂;

FIG. 5(d) is another order of mixing F₂, NO and N₂ to produce a gasmixture of F₃NO-free FNO/F₂/N₂;

FIG. 6 is a data set of F₃NO formations with 1st F₂ feeding amount (%)versus total amount of F₂;

FIG. 7 is a data set of F₃NO formations with 1st N₂ feeding amount (%)versus total amount of N₂.

FIG. 8 is FTIR signals and etch rates after SiN etched with FNO and F₂gas mixture with different F₂ mixing orders;

FIG. 9 is F₃NO formation with different N₂ mixing orders;

FIG. 10 is FTIR signals and etch rates versus FNO concentrations;

FIG. 11 is FTIR signals and etch rates versus etch time;

FIG. 12 is FTIR results of monitoring of different compositions; and

FIG. 13 is results of monitoring of etching performance.

DESCRIPTION OF PREFERRED EMBODIMENTS

Disclosed are systems and methods for storing and supplying F₃NO-freeFNO gas and F₃NO-free FNO gas mixtures, such as FNO/F₂, FNO/F₂/N₂, forusing as thermal and/or plasma dry etching gases to etch semiconductorstructures. Disclosed are also systems and methods for thermally and/orplasma dry etching semiconductor structures using F₃NO-free FNO gas andF₃NO-free FNO gas mixtures. Furthermore, disclosed are methods forproducing F₃NO-free FNO gas and F₃NO-free FNO gas mixtures for using asthermal etching gases to etch semiconductor structures. The disclosedmethods for producing F₃NO-free FNO gas and F₃NO-free FNO gas mixturesmay provide a purity of F₃NO-free FNO gas of 99% or greater, and animpurity of F₃NO less than 1%.

FNO (nitrosyl fluoride, CAS number: 7789-25-5, boiling point: −72.4° C.(−59.9° C.)) and/or a mixture of FNO with other etching gases, such asF₂, HF, cC₄F₈, C₄F₆, CF₄, CHF₃, CF₃H, CH₂F₂, COS, CS₂, CF₃I, C₂F₃I,C₂F₅I, SO₂, and the like, may be used as highly reactive fluorinatingthermal etching gases. Applicant discovered that FNO gas used forthermally etching the semiconductor structures should contain less to noF₃NO (trifluoroamine oxide, CAS number: 13847-65-9, boiling point:−87.6° C.) impurity. Thus, the disclosed F₃NO-free FNO gas contains lessto no F₃NO impurity, which refers to F₃NO-free FNO gas. F₃NO-free hereinrefers to a gas having F₃NO impurity less than 1%. F₃NO-free may alsorefer to F₃NO-less having the same definition as F₃NO-free. Insemiconductor applications, FNO may be diluted in an inert gas, such asN₂. Ar, He, Ne, Kr, Xe, or mixtures thereof, to obtain a concertation ofFNO as needed. The FNO gas mixture FNO/F₂/N₂ is one of exemplary FNO gasmixtures. When F₃NO-free FNO diluted in the inert gas, the F₃NO impurityin the mixture is even less than 1%. For instance, 15% FNO in a gasmixture of F₃NO-free FNO and N₂ may have F₃NO impurity less than 0.15%.

In semiconductor applications, FNO gas may be pre-synthesized for use asan etchant or produced in situ or in close proximity to where it is usedto etch semiconductor structures. Regarding the pre-synthesized FNO gas,a purity of 99%+FNO may be obtained and F₃NO impurity exists in FNO isless than 1% taking into account that other impurities may exist in FNOgas.

It is known that mixing F₂ and NO in situ produces FNO. However, usingF₂ and NO as starting materials to produce FNO may generate otherproducts such as, F₃NO, FNO₂, NF₃, N₂O, NO₂, etc., as byproductsexisting in the product FNO. The reactions involved in mixing NO and F₂may include the following reactions.

2NO+F₂→2FNO,

2NO+3F₂→2F₃NO,

FNO+F₂→F₃NO

N₂O+2F₂→NF₃+FNO

N₂O and NO₂ may exist in the starting material NO as impurity.

Thus, when F₂ is mixed with NO forming a gas mixture of F₂ and NO insitu at the time it is used in an etching process, besides forming thedesired FNO etching gas, oxyfluorides of nitrogen containing a groupingF—N—O, such as F₃NO, may also be formed as impurity in the gas mixtureof F₂ and NO. Applicant found that F₃NO does exist in the mixture of F₂and NO when producing FNO by mixing F₂ and NO if a ratio of F₂ to NO isnot very well controlled.

To our knowledge, so far no existing work has been mentioning thepresence of F₃NO as impurity in either pre-synthesized FNO gas and/or inthe FNO product produced in situ, such as produced by mixing F₂ and NOgas in situ. Since F₃NO has higher reactivity against Si-containingmaterials than FNO as shown in FIG. 1, for etching semiconductorstructures, the produced etching gas FNO should be free of F₃NO. F₃NOexisting in FNO etching compositions may have detrimental effects toetching processes such as, particles formed on the substrate and cracksoccurring in the substrate, which may be seen in the examples thatfollow. F₃NO existing in FNO etching compositions may also influenceetching performance, such as selectivity and etch rate controllability.Thus, a control of F₃NO formation in producing FNO is required in orderto perform a precise etching process in semiconductor industry. To thispoint, FNO used as an etching compound has to be in high purity, withminimal F₃NO levels.

In semiconductor applications, oxyfluorides of nitrogen, i.e. compoundscontaining the grouping F—N—O, such as FNO, FNO₂ and F₃NO, may becorrosive to etching gas containers and pipelines, etching chambers,substrates to be etched, etc., which may lower the semiconductor deviceperformance. In addition, materials made of containers, pipelines andcomponents along the pipelines for storage and delivery ofFNO-containing gas to an etching chamber and materials made of theetching chamber have to be compatible with FNO. This means no corrosionsand no reactions occur between FNO and the above materials that couldcause contaminations to the etching gases and the substrate to beetched. When FNO is produced from the precursors/starting materials(e.g., NO and F₂) at the time it is used as an etching gas, theprecursors may also create different storage and handling problems fromthe product FNO. As a result, when producing FNO, materialcompatibilities between starting materials (e.g., F₂ and NO) and evenFNO itself and a container (e.g., cylinder), valves, manifolds and areaction chamber along with etching performance degradation thereof withshort-term or long-term use have been concerned.

Material compatibility tests are important to determine if any componentof the disclosed F₃NO-free FNO and F₃NO-free FNO gas mixtures will reactwith materials of the container (e.g., cylinder), valves, manifolds andchamber and if any component of the disclosed F₃NO-free FNO andF₃NO-free FNO gas mixtures will degrade the etching performance thereofwith short term or long-term use. Material compatibility refers to amaterial's resistance to corrosion, rust or stains when it comes incontact with a chemical, such as F₂, NO, FNO, F₃NO, etc. At times thematerials made of the container (e.g., cylinder), valves, manifolds andchamber are exposed to these chemicals at high temperatures, forexample, higher than 20° C., and high pressures, for example, higherthan 1 atm, for thermal etching, which may enhance their degradation.

The disclosed methods for producing F₃NO-free FNO gas include mixing thestarting materials F₂ and NO by controlling mixing ratios of F₂ and NO.In order to obtain various concentrations of F₃NO-free FNO gas, an inertgas, such as N₂, Ar, Kr and Xe, preferably N₂, may be added to dilutethe produced F₃NO-free FNO gas to a target concentration of F₃NO-freeFNO gas. In addition, adding an inert gas helps reduce F₃NO formation inthe process of producing F₃NO-free FNO gas in situ referring to theExamples that follow. With the disclosed mixing methods, the formationof F₃NO during the reaction between F₂ and NO may be restrained. To ourknowledge, the disclosed mixing methods (i.e., mixing ratio) have notbeen found in the prior art for producing FNO with F₂ and NO. It isknown a direct reaction between F₂ and NO is disclosed as the simplestmethod to produce FNO. However, there is no past work mentioning F₃NO asimpurity in FNO, while Applicant discovered the presence of F₃NO fromthe reaction between F₂ and NO is detrimental to the use of FNO gas invarious etching processes. Applicant also discovered the mixing methodsof F₂ and NO with or without N₂ in order to control F₃NO amount in themixture to produce F₃NO-free FNO gas. This is beneficial for producingFNO gas with precise F₃NO impurity control.

The disclosed methods for producing F₃NO-free FNO gas mixtures includemixing the starting materials F₂ and NO by controlling mixing ratios ofF₂ and NO and then mixing with an addition gas by controlling mixingorder of F₂, NO and the additional gas. The additional gas may beselected from the group consisting of F₂, HF, cC₄F₈, C₄F₈, C₄F₆, C₅F₈,CF₄, CH₃F, CF₃H, CH₂F₂, COS, CS₂, CF₃I, C₂F₃I, C₂F₅I, CFN, SO₂, NO, O₂,cO₂, CO, NO₂, N₂O, O₃, Cl₂, H₂, HBr, and combination thereof.Preferably, the additional gas is F₂. In order to obtain variousconcentrations of F₃NO-free FNO gas in the F₃NO-free FNO gas mixture, aninert gas, such as N₂, Ar, Kr and Xe, preferably N₂, may be added todilute the produced F₃NO-free FNO gas mixture to a target concentrationof F₃NO-free FNO gas. Similarly, adding an inert gas helps reduce F₃NOformation in the process of producing F₃NO-free FNO gas mixture in situreferring to the Examples that follow. With the disclosed mixingmethods, the formation of F₃NO during the reaction between F₂, NO andthe additional gas may be restrained. To our knowledge, the disclosedmixing methods (i.e., controlling mixing ratio and controlling mixingorder) have not been found in the prior art for producing FNO gas andFNO gas mixture with F₂ and NO. Applicant discovered the mixing methodsof F₂, NO and additional gas with or without N₂ in order to control F₃NOamount in the mixture to produce F₃NO-free FNO gas mixture. This isbeneficial for producing FNO-containing gas mixture with precise F₃NOimpurity control.

The disclosed mixing methods provide processes to suppress the formationof F₃NO impurity when F₂ is mixed with NO in situ. The disclosed mixingmethods for producing F₃NO-free FNO from F₂ and NO include a step ofmixing F₂ and NO at a ratio F₂/NO equal to or less than stoichiometriccondition (F₂/NO≤½). In this way, the formation of F₃NO impurity in theproduced F₃NO-free FNO may be suppressed. The produced F₃NO-free FNO maybe further diluted in an inert gas, such as N₂, Ar, Kr and Xe,preferably N₂, to form different concentrations of F₃NO-free FNO in N₂according to application requirements.

The disclosed mixing methods for producing F₃NO-free FNO gas mixture(e.g., FNO/F₂) from F₂ and NO include a two-step of F₂ mixing process.In the first step, F₂ and NO are mixed equal to or less thanstoichiometric condition (F₂/NO≤½) to produce F₃NO-free FNO gas. In thesecond step additional F₂ is added to the produced F₃NO-free FNO gas toproduce F₃NO-free FNO and F₂ gas mixture. In this way, the formation ofF₃NO impurity in the produced F₃NO-free FNO and F₂ gas mixture may besuppressed. The produced F₃NO-free FNO and F₂ gas mixture may be furtherdiluted in an inert gas, such as N₂, Ar, Kr and Xe, preferably N₂, toform different concentrations of F₃NO-free FNO and F₂ in N₂ depending onapplication requirements.

NO gas is not stable and may contain a trace gas impurity of nitrogenoxygen compounds, such as NO₂, N₂O, or the like, resulting frominstability. Once NO mixed with F₂, the trace gas impurities may reactwith F₂ to eventually produce F₃NO in the product of FNO, as shown inthe following reaction: F₂+NO₂→F₃NO or F₂+N₂O→F₃NO. Therefore, it ishighly preferable to use high purity NO designed for low impurities likeN₂O and NO₂. In order to suppress the formation of F₃NO, NO gas usedherein to produce FNO should be pure as pure as feasible. Preferably,the purity of NO is provided at between approximately 99.9% by volumeand approximately 100.0% by volume, more preferably betweenapproximately 99.99% by volume and approximately 100.00% by volume, andeven more preferably between approximately 99.999% by volume andapproximately 100.000% by volume. In addition, NO gas may containbetween approximately 0.0% by volume and approximately 0.1% by volumetrace gas impurities with between approximately 0 ppm by volume toapproximately 600 ppm by volume of N—O containing gases other than NOgas, such as NO₂, N₂O, or the like, contained in said trace gaseousimpurities.

Since the disclosed mixing methods are capable of suppressing theformation of F₃NO, the impurity F₃NO in FNO may not impact the etchingperformance when using the disclosed F₃NO-free FNO gas as thermal and/orplasma dry etching gas.

The disclosed systems and methods also include systems and methods forstorage and delivery of F₃NO-free FNO gas and/or F₃NO-free FNO gasmixture through using compatible materials between FNO and containers,manifolds, pipelines, etching chambers, etc.

The disclosed method for storage and delivery of F₃NO-free FNO and/orF₃NO-free FNO diluted in an inert gas, such as N₂, Ar, Kr and Xe,preferably N₂, include storing a corrosive gas F₃NO-free FNO orF₃NO-free FNO/N₂ mixture in a steel cylinder made of alloy 4130X withNiP coated inner surface, and delivering the corrosive gas F₃NO-free FNOor F₃NO-free FNO/N₂ mixture to an application reactor through a manifoldassembly. An internal surface of the steel cylinder made of alloy 4130Xis coated with nickel plating, and the inner surface of the nickelplating is polished so as to have smooth surface resulting in lowmoisture content. Hereinafter, the steel cylinder made of alloy 4130Xwith an inner surface coating of nickel plating with polished innersurface of the nickel plating refers to the NiP coated steel cylinder.

A cylinder valve in fluidly communication with the cylinder and themanifold assembly is made of nickel or nickel alloy. Due to a pressuredifference between the cylinder and the application reactor, themanifold assembly is divided into a high-pressure zone in fluidlycommunication with the cylinder valve and a low-pressure zone in fluidlycommunication with the application chamber by a pressure regulator or apressure reducing device. The manifold assembly is not limited to bedivided into two pressure zones. The manifold assembly may be dividedinto multiple pressure zones each having different reduced pressures.Thus, with the multiple pressure zones, the manifold assembly is able todeliver the gas to different reaction chambers each requiring adifferent reduced pressure.

The pressure of the corrosive gas F₃NO-free FNO or F₃NO-free FNO/N₂mixture is reduced by the pressure regulator before entering thelow-pressure zone. Line components in the high-pressure zone may becomposed of high nickel content material. Line components in thelow-pressure zone may be composed of low nickel content material, metalor metal alloy. The line components in the high and low-pressure zonesinclude gas filters, pressure sensors, gas valves, mass flow controllers(MFCs), pipes, etc. The high nickel content material refers to nickelalloys that contains at least 14% nickel by weight. For example, MONEL®,INCONEL® or HASTELLOY® C-22® alloy. The low nickel content materialrefers to a material contains less than 14% nickel by weight or containsno nickel. For example, stainless steel. In this way, F₃NO impurity anddegradation of the equipment may be reduced. The NiP coated steelcylinder may be, but is not limited to, in a size ranging from 0.5 L to49 L. NiP coated steel cylinder. The cylinder valve may be a CeodeuxD306 Ni body Ni disphragm. The cylinder valve may be made of HASTELLOY®C-22® alloy, MONEL®, INCONEL®, pure nickel, or any other high nickelcontent materials.

The high-pressure zone of the manifold assembly may have a pressureranging from approximately 0.8 MPa to approximately 10 MPa, morepreferably, approximately 0.8 to approximately 3.5 MPa. The low-pressurezone of the manifold assembly may have a pressure ranging fromapproximately 0.1 MPa to approximately 0.8 MPa. The manifold assemblyincludes the following line components: the pressure regulator, pressuresensors, valves, gas filters, piping, etc. in the two pressure zones.The line components in the high-pressure zone may be composed of highnickel content materials, such as, MONEL®, INCONEL® or HASTELLOY® C.-22®alloy. The high nickel content material may contains at least 14%nickel. Typically, any material that contains 14% or higher nickel maybe used to make of the line components in the high-pressure zone,however, Fe-containing alloy, such as stainless steel (SS), may not beused. Whereas, in the low-pressure zone the line components may becomposed of low nickel content material that contains less than 14%nickel by weight or contains no nickel. The line components in thelow-pressure zone may also be made of any metal or any mental alloy,including high nickel content materials. The line components in thelow-pressure zone may be made of stainless steel.

The following are exemplary embodiments of the disclosed storage anddelivery systems for delivery of the disclosed F₃NO-free FNO gas and/orF₃NO-free FNO gas mixture into a target application reactor (e.g., anetching chamber for etching or a deposition chamber for cleaning) inwhich material compatibilities are considered.

In one embodiment, a packaging of F₃NO-free FNO gas from a cylinder to asemiconductor application, e.g., an etching chamber, is shown in FIG. 2.The packaging includes a manifold 101 that contains two pressure zones,one is a high-pressure zone 102, the other is a low-pressure zone 104.The pressure in the pressure zone 102 is higher than that in thepressure zone 104. The pressure range in the pressure zone 102 isapproximately from 0.8 MPa to 10 MPa. The pressure range in the pressurezone 104 is approximately from 0.1 MPa to 0.8 MPa. In one exemplaryembodiment, the pressure in the pressure zone 102 is 0.99 MPa; thepressure in the pressure zone 104 is 0.5 MPa. A cylinder 106 thatcontains a pressurized etching gas F₃NO-free FNO (e.g., from 0.8 MPa to3.5 MPa) is fluidly connected to the pressure zone 102 through acylinder valve 108. The F₃NO-free FNO gas stored in cylinder 106 may besynthesized using F₂ and NO as starting materials or may be apre-synthesized FNO. The F₃NO-free FNO gas stored in the cylinder 106has a purity of 99%. Alternatively, the F₃NO-free FNO gas stored in thecylinder 106 may be diluted in an inert gas (N₂, Ar, Kr and Xe), forexample, diluted in N₂ gas, forming a mixture of F₃NO-free FNO and N₂.The cylinder 106 is a carbon steel cylinder made of alloy 4130X with aninternal surface coating of nickel plating and a polished coatingsurface (i.e., NiP coated steel cylinder). The internal surface ofcoated nickel plating is important because a smooth surface may reducecontamination of moisture from air. A cylinder valve 108 controls theetching gas F₃NO-free FNO to be delivered from the pressure zone 102 tothe pressure zone 104 through a pipeline 110, where a valve 112, apressure sensor 114 and a pressure regulator 116 are fluidly connectedto the pipeline 110. The pressure sensor 114 reads the pressure in thepressure zone 102. An inert gas (e.g., N₂) may be added to the F₃NO-freeFNO gas in the pressure zone 102 to produce a diluted F₃NO-free FNO gas.For example, N₂ gas is added to the flow of F₃NO-free FNO gas through avalve 118 in the pressure zone 102 forming a mixture of F₃NO-free FNOwith N₂ therein. If the cylinder 106 contains already diluted F₃NO-freeFNO gas (e.g., 50% FNO in N₂), N₂ gas is added to the flow of thealready diluted F₃NO-free FNO gas through a valve 118 in the pressurezone 102 will have the already diluted F₃NO-free FNO gas furtherdiluted. In this way, the concentration of F₃NO-free FNO gas may beadjusted depending on application requirements. The pressure regulator116 reduces the pressure of the gas mixture of F₃NO-free FNO and N₂before the gas mixture of F₃NO-free FNO with N₂ enters the pressure zone104. A pressure sensor 120 reads the pressure in the pressure zone 104.The gas mixture of F₃NO-free FNO and N₂ from the pressure zone 102 isthen de-pressurized and forwarded to a mass flow controller 126 in thepressure zone 104 through a pipeline 130. The mass flow controller 126controls a flow rate of the gas mixture of F₃NO-free FNO and N₂ fed toan etching chamber 128 for an etching process. Valves 122 and 124 may beinstalled downstream and upstream of the mass flow controller 126.

Key materials involved in the cylinder, valves, manifolds, the chamberetc., shown in FIG. 2, include high nickel content materials includingNiP coated steel, nickel, nickel alloys, and low nickel contentmaterials including stainless steel. The F₃NO-free FNO gas was filled inthe cylinder 106 within a pressure range between approximately 0.8 toapproximately 10 MPa. The cylinder 106 may be a vessel, cylinder or anypressure container (pressure range 0.1 MPa to 10 MPa). The cylinder 106with high nickel content valve 108 is in fluidly communication with themanifold 101 including delivery line components, such as, pressureregulator, pressure sensors, valves, gas filters piping, etc., which arefluidly connected to the etching chamber 128. The cylinder 106 containsFNO gas having a purity of 99%. The cylinder 106 made of NiP coatedsteel. The cylinder 106 is a carbon steel cylinder made of alloy 4130Xwith an internal surface coating of nickel plating and the internalsurface of the nickel plating is polished.

The cylinder valve 108 may be an alloy having nickel content >14%,preferably the cylinder valve 108 is HASTELLOY® or other nickel alloys.In one exemplary embodiment, the cylinder valve 108 may specifically useHASTELLOY® materials, in which metal impurities (such as Fe, Ni, Cr, Mn)are less than 1 ng/mL. High pressure FNO or FNO/N₂ mixture is morecorrosive than low-pressure one. Thus, the high pressure FNO/N₂ mixturein a special package is designed to have a NiP coated steel cylinder 106communicate with a nickel alloy manifold 101 up to the pressureregulator 116, where the pressure regulator 116 is applied to reduce thepressure. In this way, the depressurized FNO/N₂ mixture is lesscorrosive down the low-pressure zone 104 and the etching chamber 128.With this setup, the cylinder valve 108 composed of nickel was found tohave less corrosion/powder formation. The cylinder 106 composed of NiPcoated steel has very smooth surface and lower moisture.

The packaging shown in FIG. 2 may also be used to store and deliverF₃NO-free FNO gas mixture formed by mixing F₃NO-free FNO gas with anadditional etching gas, such as F₂. In this case, the F₃NO-free FNO gasmixture is F₃NO-free FNO and F₂.

The disclosed systems for storage and delivery of F₃NO-free FNO gas andF₃NO-free FNO gas mixture (e.g., a gas mixture of F₃NO-free FNO and F₂)include a passivation process with the cylinder 106, the cylinder valve108, the low-pressure zone 104 of manifold assembly 101 to reduce metalimpurities delivery into the etching chamber 128. The passivationprocess may be done with FNO gas or F₂ gas. In the high-pressure zone102, a passivation process for the line components may or may not workdue to the high pressure. Thus, high nickel content materials areapplicable for making of the line components in the high-pressure zone.In the low-pressure zone 104, a passivation process may apply.

The disclosed systems and methods also include systems and methods ofetching semiconductor structures using the disclosed F₃NO-free FNO gasand/or F₃NO-free FNO gas mixtures. The disclosed etching systems andmethods include thermal etching, plasma dry etching including ALE(atomic layer etching), or the like. The disclosed F₃NO-free FNO gasand/or F₃NO-free FNO gas mixtures are applied to thermal and plasma dryetching processes. The disclosed F₃NO-free FNO gas may be used asetching gas alone (pure) or diluted in an inert gas, for example, N₂,Ar, He, Xe, etc. The concentration of the diluted F₃NO-free FNO may beless than 15%, preferably less than 10%, more preferably less than 5%,even more preferably less than 1%. In one embodiment, the concentrationof the diluted F₃NO-free FNO may be diluted to 0.01%. The disclosedF₃NO-free FNO gas may also be used as etching gas mixed with anadditional etching gas, such as, F₂, HF, cC₄F₈, C₄F₈, C₄F₆, C₅F₈, CF₄,CH₃F, CF₃H, CH₂F₂, COS, CS₂, CF₃I, C₂F₃I, C₂F₅I, CFN, SO₂, NO, O₂, CO₂,CO, NO₂, N₂O, O₃, CL₂, H₂, HBr, and combination thereof. Preferably, thedisclosed F₃NO-free FNO gas is used as etching gas mixed with F₂.

Exemplary other gases include, without limitation, oxidizers such as O₂,O₃, CO, CO₂, COS, NO, N₂O, NO₂, SO₂, and combinations thereof. Thedisclosed etching gases and the oxidizer may be mixed together prior tointroduction into the reaction chamber or the etching chamber.

Alternatively, the oxidizer may be introduced continuously into thereaction chamber and the etching gas introduced into the reactionchamber in pulses. Alternatively, both the oxidizer and the etching gasmay be introduced continuously into the reaction chamber. The oxidizermay comprise between approximately 0.01% by volume to approximately99.99% by volume of the mixture introduced into the chamber (with 99.99%by volume representing introduction of almost pure oxidizer for thecontinuous introduction alternative).

In one embodiment, the disclosed F₃NO-free FNO gas diluted in N₂ (i.e.,FNO/N₂) and mixed with an additional etching gas F₂ (i.e., FNO/N₂/F₂mixture). The disclosed F₃NO-free FNO gas mixtures FNO/N₂/F₂ maycomprise greater than 10% by volume of FNO, preferably greater than 15%by volume FNO.

The disclosed F₃NO-free FNO etching gas and the additional gas (e.g.,F₂) may be mixed prior to introduction to the reaction chamber. Theadditional etching gas may comprise between approximately 0.01% byvolume to approximately 99.99% by volume of the mixture introduced intothe chamber.

The disclosed F₃NO-free FNO gas are provided at equal to or greater than99% v/v by volume purity, preferably at greater than 99.99% v/v byvolume purity, and more preferably at greater than 99.999% v/v by volumepurity. The disclosed F₃NO-free FNO gas contain equal to or less than 1%by volume trace gas impurities, with less than 150 ppm by volume ofimpurity gases, such as H₂O, NO₂, N₂O and/or CO₂, contained in saidtrace gaseous impurities. Preferably, the water content in the disclosedF₃NO-free FNO gas is less than 20 ppm by weight.

The disclosed F₃NO-free FNO gas contains less than 1% by volume,preferably less than 0.1% by volume, more preferably less than 0.01% byvolume of F₃NO, which may provide precise etching performance and betterprocess repeatability.

The disclosed F₃NO-free FNO gas and F₃NO-free FNO gas mixtures may beused to thermal etch or plasma dry etch silicon-containing films, suchas SiN film, capped on top of a semiconductor structure, such as, a 3DNAND flash memory or a DRAM memory. The disclosed F₃NO-free FNO gas andF₃NO-free FNO gas mixtures may also be used to thermal etch or plasmadry etch silicon-containing films on a substrate, such as, SiN layer.The disclosed thermal etching or plasma dry etching method may be usefulin the manufacture of semiconductor devices such as NAND or 3D NANDgates or Flash or DRAM memory or transistors such as fin-shapedfield-effect transistor (FinFET), Lateral Gate-All-Around (LGAA) devicesand Vertical Gate-All-Around (VGAA) devices, Bulk complementarymetal-oxide-semiconductor (Bulk CMOS), fully depletedsilicon-on-insulator (FD-SOI) structures, Monolithich 3D (M3D). Thedisclosed F₃NO-free FNO gas and F₃NO-free FNO gas mixtures may be usedin other areas of applications, such as different front end of the line(FEOL) and back end of the line (BEOL) etch applications and low kapplications as well. Additionally, the disclosed F₃NO-free FNO gas andF₃NO-free FNO gas mixtures may also be used for etching Si in 3D throughsilicon aperture (TSV) etch applications for interconnecting memory tologic on a substrate. The disclosed F₃NO-free FNO gas and F₃NO-free FNOgas mixtures may be used to remove a layer of deposits or a film formedon the inner surface of a deposition chamber after a deposition process.Such a process refers to a cleaning process after deposition.

The disclosed etching method includes providing a reaction chamberhaving a substrate having a film disposed thereon or deposits (or film)on the internal surface of the chamber wall. The reaction chamber may beany enclosure or chamber within a device in which etching methods takeplace such as, and without limitation, any chambers or enclosures usedfor plasma etching, such as, reactive ion etching (RIE), capacitivelycoupled plasma (CCP) with single or multiple frequency RF sources,inductively coupled plasma (ICP), Electron Cyclotron Resonance (ECR) ormicrowave plasma reactors, or other types of etching systems capable ofselectively removing a portion of the silicon-containing film. Thechamber can be also a chamber for deposition process with one or moregas inlet for different precursors. The chamber for deposition usuallyhas controllable temperature on the substrate holder and may be a bufferchamber between reaction chamber and gas inlet. The pressure of chamberis controlled by pump system. Suitable pre-synthesized reaction chambersinclude but are not limited to the Applied Materials magneticallyenhanced reactive ion etcher sold at the trademark eMAX™, the LamResearch CCP reactive ion etcher dielectric etch product family sold atthe trademark 2300® FIex™ or Tokyo Electron sold at the trademarksINDY™, INDY PLUS™ and NT333™. The reaction chamber may be heated to atemperature ranging from room temperature to approximately 1000° C.Preferably from room temperature to 600° C., more preferably from 100 to300° C. Depending on application targets, the temperature may beapproximately 100° C., 500° C. or 600° C. This kind of thermal etchercan introduce molecules by different ways such as flow through, showerhead, or other design. There will be a gas outlet connecting to apumping system that controls the pressure of the chamber.

The disclosed F₃NO-free FNO gas and F₃NO-free FNO gas mixtures aresuitable for etching semiconductor structures including thermal etchingand plasma dry etching, such as, channel holes, gate trenches, staircasecontacts, capacitor holes, contact holes, etc., in thesilicon-containing films. For thermal etching, the disclosed F₃NO-freeFNO gas and F₃NO-free FNO gas mixtures may be applied for isotropicetching purpose in a thermal reactor. For plasma etching, the disclosedF₃NO-free FNO gas and F₃NO-free FNO gas mixtures are not only compatiblewith currently available mask materials but also compatible with thefuture generations of mask materials because the disclosed F₃NO-free FNOgas and mixtures induce little to no damage on the mask along with goodprofile of high aspect ratio structures. In other words, the disclosedF₃NO-free FNO gas and F₃NO-free FNO gas mixtures may produce verticaletched patterns having minimal pattern collapse or roughness.Preferably, the disclosed F₃NO-free FNO gas and F₃NO-free FNO gasmixtures etching compositions are suitably stable during the etchingprocess for delivery into the reactor/chamber.

The reaction chamber may contain one or more than one substrate. Thesubstrates may be any suitable substrates used in semiconductor,photovoltaic, flat panel or LCD-TFT device manufacturing. Examples ofsuitable substrates include wafers, such as silicon, silica, glass, orGaAs wafers. The wafer will have multiple films or layers on it fromprevious manufacturing steps, including silicon-containing films orlayers. The layers may or may not be patterned.

The disclosed F₃NO-free FNO etching gas is introduced into the reactionchamber containing the substrate. The gas may be introduced to thechamber at a flow rate ranging from approximately 0.1 sccm toapproximately 30 slm. One of ordinary skill in the art will recognizethat the flow rate may vary from tool to tool and application toapplication.

The disclosed F₃NO-free FNO etching gas may be supplied either in neatform or in a blend with an inert gas, such asN₂, Ar, He, Xe, etc. Thedisclosed F₃NO-free FNO etching gas may be present in varyingconcentrations in the blend.

FTIR, microscope analyses, pressure monitoring (pressure sensor),ellipsometer, Energy-dispersive X-ray spectroscopy (EDX), Inductivelycoupled plasma mass spectrometry (ICP-MS), analytical electronmicroscopy (AEM), X-ray photoelectron spectroscopy (XPS), ScanningElectron Microscope (SEM), Transmission electron microscopy (TEM) orother measurement tools may be used to monitor changes of compositionsand etching performance using the disclosed F₃NO-free FNO etching gas toetch the semiconductor structures, and also monitor the thermallyactivated etching gas from the chamber exhaust to determine thedegradation of materials composed of the cylinder, the cylinder valveand the line components in the manifold assembly.

The disclosed F₃NO-free FNO etching gas may be mixed with other gaseseither prior to introduction into the reaction chamber or inside thereaction chamber. Preferably, the gases may be mixed prior tointroduction to the chamber in order to provide a uniform concentrationof the entering gas.

In another alternative, the disclosed F₃NO-free FNO etching gas may beintroduced into the chamber independently of the other gases such aswhen two or more of the gases react.

In another alternative, the disclosed F₃NO-free FNO etching gas and theinert gas are the only two gases that are used during the etchingprocess.

The temperature and the pressure within the reaction chamber are held atconditions suitable for the film on the substrate to react with theetching gas. For instance, the pressure in the chamber may be heldbetween approximately 0.1 mTorr and approximately 1000 Torr, preferablybetween approximately 1 Torr and approximately 400 Torr, as required bythe etching parameters. Likewise, the substrate temperature in thechamber may range between about approximately room temperature toapproximately 1000° C. depending on the process requirements. Preferablyfrom room temperature to 600° C., more preferably from 100 to 300° C.Depending on application targets, the temperature may be approximately100° C., 500° C. or 600° C.

EXAMPLES

The following non-limiting examples are provided to further illustrateembodiments of the invention. However, the examples are not intended tobe all inclusive and are not intended to limit the scope of theinventions described herein.

In the following examples, FTIR spectra were collected with ThermoNICOLET6700 with cell length: 6.4 m; cell temperature: 40° C.; cellpressure: 10 Torr; scan: 10 times and 2 cm⁻¹ resolution. In thefollowing examples, the etching gas was selected from F₃NO-free FNO-onlyand/or F₃NO-free FNO/F₂/N₂ gas mixture. The F₃NO-free FNO/F₂/N₂ gasmixture contained about 15% F₃NO-free FNO and about 10% F₂ in N₂.

Example 1 Pre-Synthesized F₃NO-Free FNO

The pre-synthesized F₃NO-free FNO gas has a purity of 99% FNO.Impurities in the pre-synthesized F₃NO-free FNO gas may include F₃NO,NO₂, N₂O, etc. NO₂ and N₂O may come from NO cylinder aging. F₃NOimpurity is less than 1%. From the example that follows, FNO diluted inan inert gas, for example, N₂ gas, may suppress F₃NO formation whenproducing FNO in situ with F₂ and NO. Furthermore, depending onsemiconductor applications, FNO gas either mixed with one or moreaddition etching gases or diluted in an inert gas. Thus, theFNO-containing etching gas formed by the pre-synthesized F₃NO-free FNOwill contain even less F₃NO impurity. For example, if a FNO-containingetching gas formed by the pre-synthesized F₃NO-free FNO contains 15%pre-synthesized F₃NO-free FNO, the tF₃NO impurity will be less than0.15%. Thus, the FNO-containing etching gas formed by thepre-synthesized F₃NO-free FNO will contains less to no F₃NO.

Example 2 F₃NO-Free FNO Produced In Situ

Besides the pre-synthesized F₃NO-free FNO, F₃NO-free FNO F₃NO-free FNOmay be produced in situ with starting materials F₂ and NO through thereaction of F₂+2NO→2FNO. In order to suppress the formation of F₃NOimpurity in the product FNO, the reaction of F₂ and NO is atstoichiometry condition, that is, the ratio of the reactants F₂ and NOis equals to approximately ½. To ensure less to no F₃NO formed, theratio of the reactants F₂ and NO may be less than approximately ½.

The produced F₃NO-free FNO gas may be diluted in an inert gas for usingas etching gas in semiconductor applications. The inert gas may be N₂,Ar, He, Ne, Kr, Xe. In one embodiment, F₃NO-free FNO gas may be dilutedwith N₂, forming F₃NO-free FNO and N₂ gas mixture. The F₃NO-free FNO andN₂ gas mixture may be produced by mixing F₂, NO and N₂ at a molar ratioof F₂/NO≤½ with required N₂ amount depending on application requirementsof FNO concentration. The orders of mixing F₂, NO and N₂ to form theF₃NO-free FNO and N₂ gas mixture are shown in FIG. 3(a) to FIG. 3(d).The key point for the mixing orders is the ratio of F₂ to NO is atstoichiometry condition, that is, equals to approximately ½, or lessthan approximately ½. FIG. 3(a) shows the three components F₂, NO and N₂are mixed in a reactor simultaneously and then excess N₂ is added to thereactor. This is equivalent to the reactants F₂ and NO are initiallydiluted in N₂ to produce a product FNO in N₂ and the produced FNO isthen further diluted in N₂. The reaction equation is 2NO+F₂→2FNO. Withequal to or less than equivalent of F₂ in the reactants, FNO is producedand the formation of F₃NO may be controlled. For example, feeding amixture of F₂, NO and N₂, formed with 7.5 sccm F₂, 15 sccm NO and 75sccm N₂, to a reactor, where the reaction between F₂ and NO occurs toform the product FNO diluted in N₂. Since the ratio of F₂ to NO is =½,all F₂ will be consumed to produce FNO and no F₂ remains to generateF₃NO. In this way, F₃NO formation may be restrained and the produced FNOis F₃NO-free FNO. More N₂ (10 SCCM) is then added to the reactorresulting in the F₃NO-free FNO diluted in N₂, thereby forming a gasmixture of 15% F₃NO-free FNO in N₂.

Alternatively, the gas mixture of F₃NO-free FNO and N₂ may be producedby mixing F₂/N₂ and NO at a molar ration of F₂/NO ½. The order of mixingF₂, N₂ and NO is shown in FIG. 3(b). A mixture of F₂ and N₂ is formedfirst and then NO is added into the mixture, in which the reaction of F₂and NO occurs to produce FNO in N₂. Additional N₂ is then added to theproduct FNO forming FNO diluted in N₂. The reaction equation is2NO+F₂→2FNO. With equal to or less than equivalent of F₂ in thereactants, the formation of F₃NO may be controlled. For example, amixture of F₂ and N₂ is formed with 7.5 sccm F₂ and 75 sccm N₂ fed to areactor. The mixture is then mixed with 15 sccm NO in the reactor wherethe reaction between F₂ and NO occurs to form the product F₃NO-free FNO.The product F₃NO-free FNO is then diluted in N₂ with 10 SCCM N₂ forminga gas mixture of 15% FNO diluted in N₂.

Alternatively, the gas mixture of F₃NO-free FNO and N₂ may be producedby mixing F₂ and NO/N₂ at a molar ratio of F₂/NO ½. The order of mixingF₂, N₂ and NO is shown in FIG. 3(c). A mixture of NO and N₂ is formedfirst and then F₂ is added into the mixture, in which the reaction of F₂and NO occurs to produce FNO in N₂. Additional N₂ is then added to theproduct FNO forming FNO further diluted in N₂. The reaction equation is2NO+F₂→2FNO. With equal or less equivalent of F₂ in the reactants, theproduct FNO is produced and the formation of F₃NO may be controlled.

Alternatively, the gas mixture of F₃NO-free FNO and N₂ may be producedby mixing F₂/N₂ and NO/N₂ at condition of F₂/NO ½, in which F₂ and NOare diluted in N₂, respectively. The order of mixing F₂, N₂ and NO isshown in FIG. 3(d). A mixture of F₂ and N₂ is formed first and then amixture of NO and N₂ is added into the mixture of F₂ and N₂, in whichthe reaction of F₂ and NO occurs to produce FNO in N₂. Additional N₂ isthen added to the product FNO in N₂ forming a different concentration ofFNO in N₂. The reaction equation is 2NO+F₂→2FNO. With equal to or lessthan equivalent of F₂ in the reactants, the product FNO is produced andthe formation of F₃NO may be controlled.

Example 3 Stoichiometric Condition Versus F₂-Rich Condition

The resulting products from Example 2 were analyzed by FT-IR andidentified less to no trace of F₃NO in the product, since the ratio ofF₂ to NO is ½, all F₂ will be consumed to produce FNO and no F₂ remainsfor generating F₃NO. FIG. 4 is a comparison of FTIR spectra of 30% FNOin N₂ produced at stoichiometric condition and at F₂-rich condition,respectively. The upper spectrum is 30% FNO produced at stoichiometriccondition; the lower spectrum is 30% FNO produced at F₂-rich condition.No F₃NO peaks were detected if FNO is manufactured under stoichiometriccondition.

Example 4 Manufacturing Gas Mixture of F₃NO-Free FNO and F₂ in N₂ InSitu (I)

The F₃NO-free FNO gas produced in situ may be mixed with an additionaletching gas, such as, F₂, for using as etching gas in semiconductorapplications. In order to suppress the formation of F₃NO in the processof producing the gas mixture of FNO/F₂/N₂, the mixing procedure wasconducted with controlling F₂ mixing order.

The gas mixture of F₃NO-free FNO/F₂/N₂ may be produced by differentmixing orders of F₂, NO and N₂. FIG. 5(a) shows F₂, NO and N₂ are mixedtogether first and then additional N₂ is added. In order to get targetF₂ composition in the gas mixture of F₃NO-free FNO/F₂/N₂, F₂/NO ratiohas to be larger than ½. Alternatively, the gas mixture of F₃NO-freeFNO/F₂/N₂ may be produced by mixing F₂ and N₂ first, then adding NO atcondition of F₂/NO ½ to produce FNO and then adding additional F₂, andadditional N₂, as shown in FIG. 5(b). In this case, the mixing order ofN₂ and NO may be interchangeable. That is, mixing F₂ and NO first andthen adding N₂ (see parentheses). Alternatively, the gas mixture ofF₃NO-free FNO/F₂/N₂ may be produced by mixing NO and N₂ first, thenadding F₂ and then adding additional N₂, as shown in FIG. 5(c). In thiscase, F₂/NO ratio has also to be larger than ½ to reach the target F₂composition the gas mixture of F₃NO-free FNO/F₂/N₂. Alternatively, thegas mixture of F₃NO-free FNO/F₂/N₂ may be produced by mixing F₂ and N₂first, then adding a mixture of NO and N₂ at condition of F₂/NO=½ andthen adding additional N₂, as shown in FIG. 5(d). Similarly, in thiscase, F₂/NO ratio has also to be larger than ½ to reach the target F₂composition the gas mixture of F₃NO-free FNO/F₂/N₂.

The mixing orders shown in FIG. 5(a), FIG. 5(c) and FIG. 5(d) are allone step F₂ mixing procedures at F₂-rich condition. As shown in FIG. 4,under F₂-rich condition, F₃NO was produced and may not be suppressed.Mixing excess F₂ with NO in the one-step F₂ mixing procedure producesmore F₃NO than mixing F₂ and NO in the two-step F₂ mixing procedure. Themixing order shown in FIG. 5(b) is a two-step F₂ mixing procedure, whichincludes a post feeding F₂ or F₂/N₂ to target a final F₂ composition inthe gas mixture of F₃NO-free FNO/F₂/N₂. Since in the first step F₂/NO≤½and F₃NO is suppressed, adding additional amount of F₂ would not produceF₃NO. Thus, only the mixing procedure shown in FIG. 5(b) provides lessto no F₃NO generation in the gas mixture of F₃NO-free FNO/F₂/N₂.

In the processes of synthesizing the gas mixture of F₃NO-free FNO/F₂/N₂,it is discovered F₃NO generation depending on F₂ and NO feeding molarratio and F₂ mixing procedure/order. Feeding F₂ amount as needed (i.e.,stoichiometry condition) for FNO formation produces least F₃NO impurity.For producing a gas mixture of FNO/F₂/N₂, the two-step F₂ mixingprocedure is applicable. The two-step F₂ mixing procedure is i) forminga mixture of F₂ and pure NO (at least 99.9% purity) by mixing chemicalequivalent F₂ and NO first with or without dilution in N₂ and then ii)adding extra F₂ gas into the mixture with or without dilution in N₂. Bythe two-step F₂ mixing procedure, less to no F₃NO was detected throughFT-IR measurements in the formation of the gas mixture of FNO/F₂/N₂.

An example, a gas mixture of 15%-FNO and 10%-F₂ in N₂ balanced gas, wasprepared by the two-step F₂ mixing procedures as shown in FIG. 5(b) anddescribed in Table 1. N₂ and NO feedings were fixed at 10 mol and 2 mol,respectively. The ratio of 1st F₂ feeding to 2nd F₂ feeding (1stF₂/2^(nd) F₂)_(w) as varied but a total flow rate of F₂ was fixed at 2.3mol in order to target the same final composition of the FNO/F₂/N₂ gasmixture. F₃NO amount in the FNO/F₂/N₂ gas mixture was monitored withFTIR to check the effect of F₂ mixing order, as shown in FIG. 6.

TABLE 1 Mixing procedures of F₂, NO and N₂ with a fixed amount of F₂1^(st) F_(2—)% 1^(st) F₂ 1^(st) N₂ NO 2^(nd) F₂ 2^(nd) N₂ (1^(st)F₂/total F₂) (mol) (mol) (mol) 1^(st) F₂/NO (mol) (mol) 43% 1 10 2 0.51.3 0 66% 1.5 10 2 0.75 0.8 0 83% 1.9 10 2 0.95 0.4 0 100%  2.3 10 21.15 0 0

In the first step, a ratio of 1^(st) F₂/total F₂ feedings is 43% and aratio of F₂ to NO needed for FNO formation is F₂/NO=0.5. In the secondstep, a post feeding of 2^(nd) F₂ is fed to the mixture of F₂ and NO totarget the final F₂ composition (in this case, 10% F₂) in the FNO/F₂/N₂gas mixture. FIG. 6 shows that F₃NO formation changes (FTIR signals)with F₂ feeding amount (1^(st) F₂_%). With 43% 1^(st) F₂/total F₂ feed,no F₃NO was formed, because F₂/NO is at stoichiometry condition. Others,66%, 83% and 100% of 1^(st) F₂/total F₂ feed, all generate F₃NO.

Example 5 Manufacturing Gas Mixture of F₃NO-Free FNO and F₂ in N₂ InSitu (II)

A gas mixture of 3.42%-FNO and 2.31%-F₂ in N₂ balanced gas (F₃NO-freeFNO/F₂/N₂) was prepared by 2 step feedings of F₂, as shown in FIG. 5(b)with various mixing amounts of 1^(st) F₂ and 2^(nd) F₂, as described inTable 2. 1^(st) F₂, NO and 2^(nd) F₂ feedings were fixed at 1 mol, 2mol, and 1.35 mol, respectively. The ratio of 1^(st) N₂/2^(nd) N₂ wasvaried while a total flow of N₂ was fixed at 55.13 mol to target samefinal composition of the gas mixture. F₃NO amount was monitored withFTIR to check the effect of N₂ mixing order as shown in FIG. 5(b), whereN₂ was split into two feedings, 1^(st) N₂ and 2^(nd) N₂. The gas mixtureof F₃NO-free FNO/F₂/N₂ may be obtained by the reaction between premixedF₂/N₂ and NO with F₂/NO ratio at ½.

TABLE 2 Mixing procedures of F₂, N₂ and NO with a fixed amount of N₂1^(st) N_(2—)% 1^(st) F₂ 1^(st) N₂ NO 2^(nd) F₂ 2^(nd) N₂ (1^(st)N₂/total N₂) (mol) (mol) (mol) 1^(st) F₂/NO (mol) (mol)  0% 1 0 2 0.51.35 55.13 11% 1 5.85 2 0.5 1.35 49.28 42% 1 23.39 2 0.5 1.35 31.74100%  1 55.13 2 0.5 1.35 0

FIG. 7 shows F₃NO formation changes (FTIR signals) with N₂ feedings andN₂ feeding amount (1^(st) N₂)_%). Without N₂ feeding, F₃NO wasgenerated. With the increase of the ratio of 1^(st) N₂ feeding to totalN₂ feeding, F₃NO formation was getting less and less and almost nil when1^(st) N₂ feeding reached 100%. Thus, adding N₂ is beneficial forreducing F₃NO formation.

Example 6 Etching Effects with On-Site Mixing Produced F₃NO-Free FNO

The etching effects were done on SiN films using on-site mixing producedF₃NO-free FNO as etching gas.

Etching Effect of 1^(st) F₂ Feeding

F₂ was fed by two-steps, as shown in FIG. 5(b). Ratios of 1^(st) F₂ to2^(nd) F₂ varied in order to produce FNO and various mixtures of FNO andF₂ for etching SiN films. Etching conditions are as follows. Pressurewas 20 Torr; Temperature was 70° C., Etching time was 2 min, Total flowrate was 1 slm fixed; Etching composition concentrations: FNO/F₂=1.48;FNO was 3.42% fixed, F₂ was 2.31% fixed; total F₂ was 40.2 sccm. FourSiN samples (1, 2, 3 and 4) were etched with different 1^(st) F₂ feedingamounts. A total of seven SiN films, listed in Table 3 were used forvarious etching tests.

TABLE 3 SiN film samples 1^(st) Total F₂ FNO Etch time Sample F₂/totalF₂ (sccm) (%) (min) 1 43% 40.2 3.42 2 2 57% 40.2 3.42 2 3 72% 40.2 3.422 4 100%  40.2 3.42 2 5 43% 115.2 9.80 2 6 43% 40.2 3.42 5 7 100%  40.23.42 5

FIG. 8 are FTIR signals and etch rates after SiN etched with FNO and F₂gas mixture with different 1^(st) F₂ feeding amounts. Clearly, more F₃NOgenerated by more 1^(st) F₂ feeding leads to higher SiN etch rates, butnot uniform etching results on SiN film surface (not shown). Sample 1,with 43% 1^(st) F₂ feeding, had the lowest amount of F₃NO; Samples 2 and3, with 57% and 72% 1^(st) F₂ feedings, had F₃NO gradually increasing.Sample 4 with 100% 1^(st) F₂ feeding, which had no 2^(nd) F₂ feedingmeaning one step of F₂ mixing process, has the highest amount of F₃NO.For the four samples, etch rates were increased with the increase ofF₃NO. Sample 1 has the lowest F₃NO formation and good etching surface(not shown) comparing to the other three samples and the original SiNfilm. Thus, less to no F₃NO impurity in FNO or less to no F₃NO impurityin the gas mixture of FNO and F₂ benefits etching performance.

Etching Effect of N₂ Feeding

Etching conditions are as follows. Pressure was 20 Torr; Temperature was70° C.; Etching time was 2 min, Total flow rate was 1 slm fixed; Etchingcomposition concentrations: FNO/F₂=1.48; FNO was 3.42% fixed, F₂ was2.31% fixed; total N₂ was 942.7 sccm. N₂ was fed by 2 steps, as shown inFIG. 5(a) and FIG. 5(c). Ratios of 1^(st) to 2^(nd) N₂ varied to produceFNO and a mixture of FNO and F₂ to etch SiN films. As shown in FIG. 9,without N₂ dilution, F₃NO formed. Thus, N₂ dilution for F₂/NO reactionreduces F₃NO formation.

Etching Effect of FNO and F₂ Concentrations

Etching composition contained FNO and F₂. FNO concentration was variedfrom 3.42% to 9.80%. F₂ concentration was varied from 2.31% to 6.62%.Etching conditions are as follows. Pressure was 20 Torr; Temperature was70° C.; Etching time was 2 min, Total flow rate was 1 slm fixed; Etchingcomposition concentrations: FNO/F₂=1.48 with 1^(st) F₂ feeding amountsof 43% of total F₂.

As shown in FIG. 10, increasing FNO concentration does not increase F₃NOamount referring to Samples 1 and 5 in Table 3. The increase of SiN etchrate for Sample 5 is due to higher concentration of FNO than that ofSample 1. The etching surface colour for Sample 5 is quite differentfrom Sample 1 (not shown), meaning low concentration of FNO and F₂benefits the etching performance.

Effect of Etch Time

Etching conditions are as follows. Pressure was 20 Torr; Temperature was70° C.; Total flow rate was 1 slm fixed; Etching compositionconcentrations: FNO/F₂=1.48; FNO was 3.42% fixed, F₂ was 2.31% fixed;total F₂ was 40.2 sccm. Etch time varied from 2 to 5 mins. Two steps F₂mixing method, as shown in FIG. 5(b), was applied to form gas mixture ofFNO/F₂/N₂.

Referring to FIG. 11 and Table 3, samples 1 and 6 with 43% 1st F₂ hadlow F₃NO; samples 4 and 7 with 100% 1st F₂ had high F₃NO. As shown, noeffect of etch time within 5 mins on the FNO and F₃NO concentrations.

Example 7 Material Compatibility for Cylinder to Store FNO and for LineComponents at High Pressure

Material compatibility tests included testing the material compatibilitybetween etching gas mixture FNO/F₂/N₂ with the storage cylinder 106 andthe components in high-pressure zone 102 shown in FIG. 2, e.g., cylindervalve 108, pipeline 110, valve 112, pressure sensor 114 and pressureregulator 116.

The tested samples were HASTELLOY® C-22®, NiP, stainless steel gasket(such as stainless steel 316L (SS316L)) and Ni gasket at pressure 0.99MPa.

XPS results show F-penetration up to 12000 Å in a vessel made of SS316Lmaterial. Thus, SS316L material may not be compatible with the etchinggas mixture FNO/F₂/N₂.

XPS results show F-penetration up to approximately 6000 Å in a vesselmade of HASTELLOY® C-22® material. Material HASTELLOY® C-22® is betterthan SS316L.

XPS results show F-penetration less than approximately 50 Å in a vesselmade of NiP coated steel material. Thus, NiP coated steel material iscompatible with the etching gas mixture FNO/F₂/N₂.

XPS results show F-penetration less than approximately 800 Å in a vesselmade of nickel material. Although nickel material is not as good as NiPcoated steel material, nickel material is somewhat compatible with theetching gas mixture FNO/F₂/N₂.

In summary, in the high-pressure zone (e.g., 0.99 MPa), NiP coated steelis good for making cylinder body. Pure nickel or nickel alloys may beused for cylinder valve. Other line components (e.g., pressureregulator, valves, gas filter, piping) in high-pressure zone may usenickel alloys, such as, HASTELLOY® C-22® including MONEL® or INCONEL®,which contain high Ni content may be preferred. Passivation process withF₂ or FNO may be applied in the high-pressure zone. The passivationprocess includes a process that elevates pressure gradually.

Example 8 Material Compatibility Tests for Line Components atLow-Pressure

Material compatibility tests also included testing the materialcompatibility between etching gas mixture FNO/F₂/N₂ and the componentsin low-pressure zone 104 shown in FIG. 2, e.g., pressure sensor 120,pipeline 130, valves 122 and 124.

SS316L & Ni Material Compatibility

The vessels used herein were Ni vessels each containing a Ni gasketsample and one or two SS gasket (i.e., SS316L gasket) samples. Thesamples were tested at 0.50 MPa with the etching gas F₃NO-free FNO/F₂/N₂in periods of 17 days and 21 days.

SS samples were covered with particles and corrosion was observed whenexposed to F₃NO free FNO/F₂/N₂. Thus, SS sample is not compatible withF₃NO-free FNO/F₂/N₂ even at low-pressure. No corrosion was observed onthe nickel samples.

For FNO-only, SS sample was found compatible with FNO-only atlow-pressure with no observed corrosion however for F₃NO-free FNO/F₂/N₂it was found not as compatible in the low pressure zone. However, afterpassivation using F₂ or FNO, SS sample may be compatible with theetching gas F₃NO-free FNO/F₂/N₂ in the low-pressure zone. Alternatively,if the etching gas does not contains F₂, SS is suitable for making theline components in the low-pressure zone.

FNO and F₂ with Low Level of F₃NO or F₃NO-Free

Two SS samples were installed in each of three vessels, respectively, at0.5 MPa for 20 days. One vessel was fed with FNO-only, the other twowere fed with the gas mixture of 15% F₃NO-free FNO and 10% F₂ in N₂ andhalf concentration of the gas mixture of 15% F₃NO-free FNO and 10% F₂ inN₂, for comparison. Even with F₃NO-free, the gas mixture of 15%F₃NO-free FNO and 10% F₂ in N₂ resulted in corrosion on SS316L at 0.5MPa, but no corrosion with FNO only on SS316L surface. SS316L is notcompatible with the gas mixture of 15% F₃NO-free FNO and 10% F₂ in N₂.Thus, F₂ or FNO passivation in low-pressure zone for F₃NO-free F₂/FNO/N₂is needed. SS316L may be compatible with the etching gas F₃NO-freeFNO/F₂/N₂ after F₂ or FNO passivation. SS316L may be compatible with thegas mixture of FNO and N₂ without F₂.

Example 9 Material Compatibility Summary

The material compatibility test conditions and results for both highpressure and low-pressure zones are listed in Table 4. In summary, highcontent nickel materials including NiP coated steel, pure nickel ornickel alloys, may be compatible with high-pressure zone. SS316L iscompatible with FNO and N₂ gas mixture in the low-pressure zone.However, with F₂ or FNO passivation, SS316L may be compatible withFNO/F₂/N₂ gas mixture in the low-pressure zone. Furthermore, metals,metal alloys without nickel content or metal alloys with high nickelcontent or low nickel content may compatible with the low-pressure zone.

TABLE 4 Material compatibility summary F₂ (%) 10.5 10.5 10.5 5.3 10.55.3 0 FNO (%) 14.5 14.5 14.5 7.3 14.5 7.3 14.5 F₃NO Exist Exist ExistExist free free free Pressure (MPa) 0.99 0.99 0.50 0.50 0.50 0.50 0.50Total duration (days) 7 21 21 43 20 20 20 Non-coated steel C C — — — — —SS316L — C C  C  C  C  A  NiP coated steel — A A* A* A* A* A* Nickel — BB  B* B* B* B* HASTELLOY ® — B B* B* B* B* B* C-22 ®

Note in Table 4, “A” means excellent compatibility or good to use; “A*”means excellent compatibility or good to use but actual tests were notdone; “B” means acceptable with limitations or limited; “B*” meansacceptable with limitations or limited but actual tests were not done;“C” means poor or not compatible; “-” means no actual tests. Thenon-coated steel may be any type of steel with a NiP coating on thesurface, such as Mn-steel. The SS316L contains up to 14% nickel.

Example 10 Stability (Shelf Life) Test

A 10 L size NiP coated steel cylinder and a Ceodeux D306 Ni body Nidiaphragm cylinder valve were used for stability test. The cylinder waspre-treated with vacuum baking first and then passivated with F₂. 15%FNO/N₂ by mixing F₂, NO and N₂ as described in Example 3 was filled tothe 10 L size NiP coated steel cylinder at 0.99 MPa(G). The shelf lifetest was done by monitoring FNO and impurities (NO₂, HF, F₃NO) withFT-IR for 6 months. The etching performance test was done byperiodically checking SiN etch rate for 6 months and the stability ofthe product was confirmed up to 6 months in terms of composition and SiNetching performance.

FIG. 12 is the results of monitoring of different composition by FT-IR.FIG. 13 is the results of monitoring of etching performance over time.The etching performance was done with the etching gas of 20% F₂ and 1%FNO at temperature 100° C., pressure 20 Torr. The etching time was 1min. The results from FIG. 12 and FIG. 13 show no significantconcentration changes on FNO and impurities and no significant etchingperformance changes, meaning that 6-month stability is solid andlong-term stability is promising.

Example 11 Storage and Supply Packaging for F₃NO-Free FNO-Containing Gas

Referring to FIG. 2, a packaging for storage and supply of F₃NO-freeFNO-containing gas for thermal and plasma dry etching applications orthe like in semiconductor industry may include a NiP coated steelcylinder for storage of F₃NO-free FNO-containing gas. The NiP coatedsteel cylinder may be a carbon steel cylinder made of alloy 4130X withan internal surface coating of nickel plating (NiP) and a polishedsurface of NiP coating. The supply packaging further include a nickelcylinder valve for controlling delivery of the F₃NO-free FNO-containinggas from the NiP coated steel cylinder to a manifold assembly that has ahigh-pressure zone and a low-pressure zone divided by a pressureregulator. Line components in the high-pressure zone are made of highnickel content material/alloy having at least 14% nickel by weight. Theline components in the high-pressure zone include pressure regulator,valves, gas filter, piping, pressure sensors, or the like. The highnickel content alloy may be MONEL®, INCONEL®, HASTELLOY® C-22® or thelike. The high-pressure zone may be passivated with F₂ or FNO withgradually increasing the pressure. Line components in the low-pressurezone may be made of any metal or any metal alloy including high nickelcontent material/alloy, low nickel content material/alloy or no nickelcontent material/alloy, for example, stainless steel. The low-pressurezone may be passivated with F₂ or FNO.

With pre-synthesized F₃NO-free FNO (F₃NO impurity is less than 1%)on-site, FNO and N₂ may be mixed in situ to produce F₃NO-free FNO/N₂ gasmixture with various concentrations of FNO in N₂. Thus, F₃NO-free FNOgas may be diluted in N₂ and stored in the NiP coated steel cylinder.The concentration of FNO in the mixture of F₃NO-free FNO/N₂ may rangefrom approximately 0.01% to approximately 80%. Preferably, theconcentration of FNO in the mixture of F₃NO-free FNO/F₂/N₂ may rangefrom approximately 0.01% to approximately 30%. In one embodiment, theconcentration of FNO in the mixture of F₃NO-free FNO/N₂ is approximately3%. In another embodiment, the concentration of FNO in the mixture ofF₃NO-free FNO/N₂ is approximately 15%.

With pre-synthesized F₃NO-free FNO (F₃NO impurity is less than 1%)on-site, FNO and F₂ may be mixed in situ to produce F₃NO-free FNO/F₂/N₂gas mixture with various concentrations of FNO and F₂ in N₂. Theconcentration of FNO in the mixture of F₃NO-free FNO/F₂/N₂ may rangefrom approximately 0.01% to approximately 80% and the concentration ofF₂ in the mixture of F₃NO-free FNO/F₂/N₂ may range from approximately 0%(no F₂) to approximately 80%. Preferably, the concentration of FNO inthe mixture of F₃NO-free FNO/F₂/N₂ may range from approximately 0.01% toapproximately 30% and the concentration of F₂ in the mixture ofF₃NO-free FNO/F₂/N₂ may range from approximately 0% to approximately20%.

In one embodiment, the concentration of FNO in the mixture of F₃NO-freeFNO/F₂/N₂ is approximately 15% and the concentration of F₂ in themixture of F₃NO-free FNO/F₂/N₂ is approximately 10%. F₃NO-free FNO gasmay be diluted in N₂ and stored in the NiP coated steel cylinder first.Then either pure F₂ or diluted F₂ in N₂ is mixed with the dilutedF₃NO-free FNO producing F₃NO-free approximately 15% FNO andapproximately 10% F₂ in N₂ gas mixture for use as etching gas insemiconductor applications. The produced F₃NO-free approximately 15% FNOand approximately 10% F₂ in N₂ gas mixture may be stored in the NiPcoated steel cylinder. The advantages of supplying pre-synthesizedF₃NO-free FNO for producing the gas mixture of F₃NO-free FNO/F₂/N₂ arei) no exothermic reaction by mixing FNO and F₂; ii) less to no impurityF₃NO generated; iii) better reproducibility of etching performance shownin the above examples.

Alternatively, the F₃NO-free FNO/F₂/N₂ gas mixture may be produced insitu by mixing NO (purity at least 99.9%) and F₂ gases with two-step F₂mixing method as described above in Example 3. The produced F₃NO-freeFNO/F₂/N₂ gas mixture may be stored in a NiP coated steel cylinder foruse as etching gas or other purposes in semiconductor applications. Theadvantages of producing F₃NO-free FNO/F₂/N₂ gas mixture by mixing NO andF₂ is the concentration of FNO in the F₃NO-free FNO/F₂/N₂ gas mixturemay be adjustable depending on requirements of etching applications.

It will be understood that many additional changes in the details,materials, steps, and arrangement of parts, which have been hereindescribed and illustrated in order to explain the nature of theinvention, may be made by those skilled in the art within the principleand scope of the invention as expressed in the appended claims. Thus,the present invention is not intended to be limited to the specificembodiments in the examples given above and/or the attached drawings.

While embodiments of this invention have been shown and described,modifications thereof may be made by one skilled in the art withoutdeparting from the spirit or teaching of this invention. The embodimentsdescribed herein are exemplary only and not limiting. Many variationsand modifications of the composition and method are possible and withinthe scope of the invention. Accordingly, the scope of protection is notlimited to the embodiments described herein, but is only limited by theclaims which follow, the scope of which shall include all equivalents ofthe subject matter of the claims.

1. A system for storage and supply of a F₃NO-free FNO-containing gas,the system comprising: a NiP coated steel cylinder with a polished innersurface, configured and adapted to store the F₃NO-free FNO-containinggas; a cylinder valve, in fluid communication with the cylinder,configured and adapted to release the F₃NO-free FNO-containing gas fromthe cylinder; and a manifold assembly, comprising a pressure regulatorand line components, downstream of the cylinder valve, configured andadapted to deliver the F₃NO-free FNO-containing gas to a target reactor;wherein the pressure regulator is configured and adapted tode-pressurize the F₃NO-free FNO-containing gas in the manifold assemblyso as to divide the manifold assembly into a first pressure zoneupstream of the pressure regulator and a second pressure zone downstreamof the pressure regulator.
 2. The system of claim 1, wherein F₃NO-freeFNO contained in the F₃NO-free FNO-containing gas has less thanapproximately 1% F₃NO by volume.
 3. The system of claim 2, wherein theF₃NO-free FNO-containing gas is selected from the group consisting ofF₃NO-free FNO gas, a mixture of the F₃NO-free FNO gas with an inert gas,a mixture of the F₃NO-free FNO gas with an additional gas and a mixtureof the F₃NO-free FNO gas with the inert gas and the additional gas. 4.The system of claim 3, wherein the inert gas is N₂, Ar, He, Ne, Kr, Xe,or mixtures thereof.
 5. The system of claim 4, wherein the additionalgas is selected from the group consisting of F₂, HF, cC₄F₈, C₄F₈, C₄F₆,C₅F₈, CF₄, CH₃F, CF₃H, CH₂F₂, COS, CS₂, CF₃I, C₂F₃I, C₂F₅I, CFN, SO₂,NO, O₂, CO₂, CO, NO₂, N₂O, O₃, Cl₂, H₂, HBr, and combination thereof. 6.The system of claim 5, wherein the F₃NO-free FNO-containing gas is a gasmixture of F₃NO-free FNO gas, F₂ and N₂ for etch films.
 7. The system ofclaim 1, wherein the cylinder valve, the pressure regulator and linecomponents in the first pressure zone are made of nickel containingmaterial having at least 14% nickel by weight.
 8. A method for storageand supply of a F₃NO-free FNO-containing gas, the method comprising thesteps of: storing the F₃NO-free FNO-containing gas in a NiP coated steelcylinder with a polished inner surface; releasing the F₃NO-freeFNO-containing gas from the cylinder to a manifold assembly byactivating a cylinder valve in fluid communication with the cylinder andthe manifold assembly; de-pressurizing the F₃NO-free FNO-containing gasby activating a pressure regulator in the manifold assembly so as todivide the manifold assembly into a first pressure zone upstream of thepressure regulator and a second pressure zone downstream of the pressureregulator; and feeding the de-pressurized F₃NO-free FNO-containing gasto a target reactor downstream of the second pressure zone.
 9. Themethod of claim 8, further comprising the step of producing F₃NO-freeFNO contained in the F₃NO-free FNO-containing gas by mixing NO and F₂gases at a ratio of F₂ gas to NO gas less than or equal to ½ and apurity of NO gas at least 99.9% by volume, wherein the producedF₃NO-free FNO contains less than approximately 1% F₃NO by volume. 10.The method of claim 9, wherein the F₃NO-free FNO-containing gas is a gasmixture of F₃NO-free FNO gas, F₂ and N₂ for etch films produced by thesteps of mixing the produced F₃NO-free FNO gas with an additional amountof F₂ to produce the gas mixture of the F₃NO-free FNO gas and F₂; anddiluting the gas mixture of the F₃NO-free FNO gas and F₂ in N₂ to formthe gas mixture of F₃NO-free FNO gas, F₂ and N₂.
 11. The method of claim8, further comprising the step of passivating the manifold assembly withF₂ or FNO.
 12. The method of claim 8, wherein the cylinder valve, thepressure regulator and line components in the first pressure zone aremade of nickel containing material having at least 14% nickel by weight.13. An etching system, the system comprising a reactor, configured andadapted to provide a film to be etched therein, the film being on asubstrate held inside the reactor or on the inner surface of thereactor; a NiP coated steel cylinder, configured and adapted to store apressurized etching gas F₃NO-free FNO; a cylinder valve, in fluidcommunication with the cylinder, configured and adapted to release theetching gas F₃NO-free FNO from the NiP coated steel cylinder; and amanifold assembly, comprising a pressure regulator and line components,downstream of the cylinder valve, configured and adapted to deliver theetching gas F₃NO-free FNO to the reactor; wherein the pressure regulatorin the manifold assembly is configured and adapted to de-pressurize theetching gas F₃NO-free FNO so as to divide the manifold assembly into afirst pressure zone upstream of the pressure regulator and a secondpressure zone downstream of the pressure regulator.
 14. The etchingsystem of claim 13, wherein the F₃NO-free FNO gas contains less thanapproximately 1% F₃NO by volume.
 15. The etching system of claim 13,further comprising a first gas line parallel to the manifold assembly,the first gas line feeding an additional etching gas to the NiP coatedsteel cylinder or the etching chamber, wherein the additional etchinggas is selected from the group consisting of F₂, HF, cC₄F₈, C₄F₈, C₄F₆,C₅F₈, CF₄, CH₃F, CF₃H, CH₂F₂, COS, CS₂, CF₃I, C₂F₃I, C₂F₅I, CFN, SO₂,NO, O₂, CO₂, CO, NO₂, N₂O, O₃, Cl₂, H₂, HBr, and combination thereof, toform a first etching composition with F₃NO-free FNO gas.
 16. The etchingsystem of claim 15, further comprising a second gas line for feeding aninert gas to the NiP coated steel cylinder or the first pressure zone ofthe manifold assembly, wherein the F₃NO-free FNO gas is mixed with theinert gas to produce a diluted F₃NO-free FNO gas, wherein the inert gasis N₂, Ar, He, Ne, Kr, Xe, or mixtures thereof, to form a second etchingcomposition with F₃NO-free FNO gas and the additional etching gas. 17.The etching system of claim 16, wherein the second etching compositionis a gas mixture of F₃NO-free FNO gas, F₂ and N₂.
 18. The etching systemof claim 13, wherein the cylinder valve, the pressure regulator and theline components in the first pressure zone are made of nickel containingmaterial having 14% nickel by weight.
 19. The etching system of claim13, wherein the line components in the second pressure zone is made of ametal or a metal alloy.
 20. A gaseous composition for semiconductorapplications, the gaseous composition comprising F₃NO-free FNO gascontaining less than approximately 1% F₃NO impurity by volume; and aninert gas being capable of suppressing the concentration of F₃NOimpurity in the F₃NO-free FNO gas.